arm64: dts: imx8mm-prt8mm: update 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-prt8mm.dts

@@ -264,7 +264,7 @@ MX8MM_IOMUXC_NAND_CE1_B_USDHC3_STROBE		0x190
 		>;
 	};
 
-	pinctrl_usdhc3_100mhz: usdhc3grp100mhz {
+	pinctrl_usdhc3_100mhz: usdhc3-100mhzgrp {
 		fsl,pins = <
 			MX8MM_IOMUXC_NAND_WE_B_USDHC3_CLK		0x194
 			MX8MM_IOMUXC_NAND_WP_B_USDHC3_CMD		0x1d4
@@ -280,7 +280,7 @@ MX8MM_IOMUXC_NAND_CE1_B_USDHC3_STROBE		0x194
 		>;
 	};
 
-	pinctrl_usdhc3_200mhz: usdhc3grp200mhz {
+	pinctrl_usdhc3_200mhz: usdhc3-200mhzgrp {
 		fsl,pins = <
 			MX8MM_IOMUXC_NAND_WE_B_USDHC3_CLK		0x196
 			MX8MM_IOMUXC_NAND_WP_B_USDHC3_CMD		0x1d6