arm64: dts: imx8mq: Align iomuxc node name

Node name should be generic, use "pinctrl" instead of "iomuxc"
for all i.MX8M SoCs.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mq.dtsi

@@ -521,7 +521,7 @@ lcdif: lcd-controller@30320000 {
 				status = "disabled";
 			};
 
-			iomuxc: iomuxc@30330000 {
+			iomuxc: pinctrl@30330000 {
 				compatible = "fsl,imx8mq-iomuxc";
 				reg = <0x30330000 0x10000>;
 			};