arm64: dts: imx8mq-evk: Align pin configuration group names with schema

Device tree schema expects pin configuration groups to end with 'grp'
suffix, otherwise dtbs_check complain with a warning like:

    ... do not match any of the regexes: 'grp$', 'pinctrl-[0-9]+'
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mq-evk.dts

@@ -407,7 +407,7 @@ MX8MQ_IOMUXC_NAND_DATA03_QSPI_A_DATA3	0x82
 		>;
 	};
 
-	pinctrl_reg_usdhc2: regusdhc2grpgpio {
+	pinctrl_reg_usdhc2: regusdhc2gpiogrp {
 		fsl,pins = <
 			MX8MQ_IOMUXC_SD2_RESET_B_GPIO2_IO19		0x41
 		>;