arm64: dts: imx8mm-kontron: Use the VSELECT signal to switch SD card IO voltage

It turns out that it is not necessary to declare the VSELECT signal as
GPIO and let the PMIC driver set it to a fixed high level. This switches
the voltage between 3.3V and 1.8V by setting the PMIC register for LDO5
accordingly.

Instead we can do it like other boards already do and simply mux the
VSELECT signal of the USDHC interface to the pin. This makes sure that
the correct voltage is selected by setting the PMIC's SD_VSEL input
to high or low accordingly.
Reported-by: NHeiko Thiery <heiko.thiery@gmail.com>
Signed-off-by: NFrieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: NHeiko Thiery <heiko.thiery@gmail.com>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-kontron-bl.dts

@@ -321,6 +321,7 @@
 			MX8MM_IOMUXC_SD2_DATA2_USDHC2_DATA2		0x1d0
 			MX8MM_IOMUXC_SD2_DATA3_USDHC2_DATA3		0x1d0
 			MX8MM_IOMUXC_SD2_CD_B_GPIO2_IO12		0x019
+			MX8MM_IOMUXC_GPIO1_IO04_USDHC2_VSELECT		0x1d0
 		>;
 	};
 
@@ -333,6 +334,7 @@
 			MX8MM_IOMUXC_SD2_DATA2_USDHC2_DATA2		0x1d4
 			MX8MM_IOMUXC_SD2_DATA3_USDHC2_DATA3		0x1d4
 			MX8MM_IOMUXC_SD2_CD_B_GPIO2_IO12		0x019
+			MX8MM_IOMUXC_GPIO1_IO04_USDHC2_VSELECT		0x1d0
 		>;
 	};
 
@@ -345,6 +347,7 @@
 			MX8MM_IOMUXC_SD2_DATA2_USDHC2_DATA2		0x1d6
 			MX8MM_IOMUXC_SD2_DATA3_USDHC2_DATA3		0x1d6
 			MX8MM_IOMUXC_SD2_CD_B_GPIO2_IO12		0x019
+			MX8MM_IOMUXC_GPIO1_IO04_USDHC2_VSELECT		0x1d0
 		>;
 	};
 };

arch/arm64/boot/dts/freescale/imx8mm-kontron-sl.dtsi

@@ -86,7 +86,6 @@
 		pinctrl-0 = <&pinctrl_pmic>;
 		interrupt-parent = <&gpio1>;
 		interrupts = <0 IRQ_TYPE_LEVEL_LOW>;
-		sd-vsel-gpios = <&gpio1 4 GPIO_ACTIVE_HIGH>;
 
 		regulators {
 			reg_vdd_soc: BUCK1 {
@@ -229,7 +228,6 @@
 	pinctrl_pmic: pmicgrp {
 		fsl,pins = <
 			MX8MM_IOMUXC_GPIO1_IO00_GPIO1_IO0		0x141
-			MX8MM_IOMUXC_GPIO1_IO04_GPIO1_IO4		0x141
 		>;
 	};