arm64: dts: imx8mm-nitrogen-r2: add FlexSPI

Add FlexSPI description an pin muxing.
Signed-off-by: Adrien Grassein <adrien.grassein@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-nitrogen-r2.dts

@@ -72,6 +72,12 @@ ethphy0: ethernet-phy@4 {
 	};
 };
 
+&flexspi {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_flexspi>;
+	status = "okay";
+};
+
 &i2c1 {
 	clock-frequency = <100000>;
 	pinctrl-names = "default";
@@ -354,6 +360,17 @@ MX8MM_IOMUXC_NAND_READY_B_GPIO3_IO16		0x159
 		>;
 	};
 
+	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_hog: hoggrp {
 		fsl,pins = <
 			MX8MM_IOMUXC_GPIO1_IO03_GPIO1_IO3 0x09