imxrt:uart: Add PINs init for each uart port

Add PINs init function based on the selected UART port.

In general, user should configure all necessary PINs based on
the specific imxrt board in:
    bsp/imxrt/xxxx/board/MCUX_Config/pin_mux.c
There is a convenient GUI tool named MCUXpresso Config Tools,
it's free and can be obtained from NXP offical website. Open
the file:
    bsp/imxrt/imxrt1052-nxp-evk/board/MCUX_Config/MCUX_Config.mex
with MCUXpresso Config Tools, set the necessary PINs (or clocks)
and generate the new code of pin_mux.c (or clock_config.c), the
project can get right configurations based on specific imxrt
board.

But, there is no relation between RT-Thread Kconfig and MCUXpresso
Config Tools. User selects one driver in RT-Thread menuconfig, then
the ping_mux.c should be udpated by MCUXpresso Config Tools to set
the right PIN configurations for the selected driver. It's clear
but a little complex.

We add the PIN init functions for some drivers in the board.c file,
1. It's convenient to usr a driver in RT-Thread. Just select the
   driver, then the code will include all necessary parts, and the
   driver can work well.
2. User can also configure the PINs with MCUXpresso Config Tools.
3. The drivers in bsp/imxrt/libraries/drivers are common for all
   imxrt boards. They may have different PIN configurations based
   on different hardware design. So we put the PIN init functions
   in each board.c file following each different imxrt board.
Signed-off-by: NGavin Liu <gavin-liugang@outlook.com>

bsp/imxrt/imxrt1052-nxp-evk/board/board.c

@@ -12,6 +12,7 @@
 #include <rtthread.h>
 #include "board.h"
 #include "pin_mux.h"
+#include "fsl_iomuxc.h"
 
 #ifdef BSP_USING_DMA
 #include "fsl_dmamux.h"
@@ -109,6 +110,148 @@ void imxrt_dma_init(void)
     EDMA_Init(DMA0, &config);
 }
 #endif
+
+#ifdef BSP_USING_LPUART
+void imxrt_uart_pins_init(void)
+{
+#ifdef BSP_USING_LPUART1
+
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_AD_B0_12_LPUART1_TX,        /* GPIO_AD_B0_12 is configured as LPUART1_TX */
+            0U);                                    /* Software Input On Field: Input Path is determined by functionality */
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_AD_B0_13_LPUART1_RX,        /* GPIO_AD_B0_13 is configured as LPUART1_RX */
+            0U);                                    /* Software Input On Field: Input Path is determined by functionality */
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_AD_B0_12_LPUART1_TX,        /* GPIO_AD_B0_12 PAD functional properties : */
+            0x10B0u);                               /* Slew Rate Field: Slow Slew Rate
+                                                     Drive Strength Field: R0/6
+                                                     Speed Field: medium(100MHz)
+                                                     Open Drain Enable Field: Open Drain Disabled
+                                                     Pull / Keep Enable Field: Pull/Keeper Enabled
+                                                     Pull / Keep Select Field: Keeper
+                                                     Pull Up / Down Config. Field: 100K Ohm Pull Down
+                                                     Hyst. Enable Field: Hysteresis Disabled */
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_AD_B0_13_LPUART1_RX,        /* GPIO_AD_B0_13 PAD functional properties : */
+            0x10B0u);                               /* Slew Rate Field: Slow Slew Rate
+                                                     Drive Strength Field: R0/6
+                                                     Speed Field: medium(100MHz)
+                                                     Open Drain Enable Field: Open Drain Disabled
+                                                     Pull / Keep Enable Field: Pull/Keeper Enabled
+                                                     Pull / Keep Select Field: Keeper
+                                                     Pull Up / Down Config. Field: 100K Ohm Pull Down
+                                                     Hyst. Enable Field: Hysteresis Disabled */
+#endif
+#ifdef BSP_USING_LPUART2
+
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_AD_B1_02_LPUART2_TX,
+            0U);
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_AD_B1_03_LPUART2_RX,
+            0U);
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_AD_B1_02_LPUART2_TX,
+            0x10B0u);
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_AD_B1_03_LPUART2_RX,
+            0x10B0u);
+
+#endif
+#ifdef BSP_USING_LPUART3
+
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_AD_B1_06_LPUART3_TX,
+            0U);
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_AD_B1_07_LPUART3_RX,
+            0U);
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_AD_B1_06_LPUART3_TX,
+            0x10B0u);
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_AD_B1_07_LPUART3_RX,
+            0x10B0u);
+#endif
+#ifdef BSP_USING_LPUART4
+
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_B1_00_LPUART4_TX,
+            0U);
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_B1_01_LPUART4_RX,
+            0U);
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_B1_00_LPUART4_TX,
+            0x10B0u);
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_B1_01_LPUART4_RX,
+            0x10B0u);
+#endif
+#ifdef BSP_USING_LPUART5
+
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_B1_12_LPUART5_TX,
+            0U);
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_B1_13_LPUART5_RX,
+            0U);
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_B1_12_LPUART5_TX,
+            0x10B0u);
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_B1_13_LPUART5_RX,
+            0x10B0u);
+#endif
+#ifdef BSP_USING_LPUART6
+
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_AD_B0_02_LPUART6_TX,
+            0U);
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_AD_B0_03_LPUART6_RX,
+            0U);
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_AD_B0_02_LPUART6_TX,
+            0x10B0u);
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_AD_B0_03_LPUART6_RX,
+            0x10B0u);
+#endif
+#ifdef BSP_USING_LPUART7
+
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_EMC_31_LPUART7_TX,
+            0U);
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_EMC_32_LPUART7_RX,
+            0U);
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_EMC_31_LPUART7_TX,
+            0x10B0u);
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_EMC_32_LPUART7_RX,
+            0x10B0u);
+#endif
+#ifdef BSP_USING_LPUART8
+
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_AD_B1_10_LPUART8_TX,
+            0U);
+        IOMUXC_SetPinMux(
+            IOMUXC_GPIO_AD_B1_11_LPUART8_RX,
+            0U);
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_AD_B1_10_LPUART8_TX,
+            0x10B0u);
+        IOMUXC_SetPinConfig(
+            IOMUXC_GPIO_AD_B1_11_LPUART8_RX,
+            0x10B0u);
+#endif
+}
+#endif /* BSP_USING_LPUART */
+
 /**
  * This function will initial rt1050 board.
  */
@@ -121,6 +264,10 @@ void rt_hw_board_init()
     NVIC_SetPriorityGrouping(NVIC_PRIORITYGROUP_4);
     SysTick_Config(SystemCoreClock / RT_TICK_PER_SECOND);
 
+#ifdef BSP_USING_LPUART
+    imxrt_uart_pins_init();
+#endif
+
 #ifdef BSP_USING_DMA
     imxrt_dma_init();
 #endif