arm64: dts: imx8mm-beacon-som: Add QSPI NOR flash support

imx8mm-beacon-som has a Quad-SPI NOR flash connected to the FlexSPI bus.

This patch enables the FlexSPI bus and configures it to work with the
flash part.
Signed-off-by: NAdam Ford <aford173@gmail.com>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-beacon-som.dtsi

@@ -75,6 +75,22 @@
 	};
 };
 
+&flexspi {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_flexspi>;
+	status = "okay";
+
+	flash@0 {
+		reg = <0>;
+		#address-cells = <1>;
+		#size-cells = <1>;
+		compatible = "jedec,spi-nor";
+		spi-max-frequency = <80000000>;
+		spi-tx-bus-width = <4>;
+		spi-rx-bus-width = <4>;
+	};
+};
+
 &i2c1 {
 	clock-frequency = <400000>;
 	pinctrl-names = "default";
@@ -302,6 +318,17 @@
 			>;
 		};
 
+		pinctrl_flexspi: flexspigrp {
+			fsl,pins = <
+				MX8MM_IOMUXC_NAND_ALE_QSPI_A_SCLK               0x1c2
+				MX8MM_IOMUXC_NAND_CE0_B_QSPI_A_SS0_B            0x82
+				MX8MM_IOMUXC_NAND_DATA00_QSPI_A_DATA0           0x82
+				MX8MM_IOMUXC_NAND_DATA01_QSPI_A_DATA1           0x82
+				MX8MM_IOMUXC_NAND_DATA02_QSPI_A_DATA2           0x82
+				MX8MM_IOMUXC_NAND_DATA03_QSPI_A_DATA3           0x82
+			>;
+		};
+
 		pinctrl_pmic: pmicirqgrp {
 			fsl,pins = <
 				MX8MM_IOMUXC_GPIO1_IO03_GPIO1_IO3	0x141