arm64: dts: imx8mm-ddr4-evk: update gpmi pinctrl to match dtschema

The dtschema requires 'grp' in the end, so update the name.
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-ddr4-evk.dts

@@ -28,7 +28,7 @@ &gpmi {
 };
 
 &iomuxc {
-	pinctrl_gpmi_nand: gpmi-nand {
+	pinctrl_gpmi_nand: gpminandgrp {
 		fsl,pins = <
 			MX8MM_IOMUXC_NAND_ALE_RAWNAND_ALE		0x00000096
 			MX8MM_IOMUXC_NAND_CE0_B_RAWNAND_CE0_B		0x00000096