arm64: dts: imx8mm-evk: remove orphaned pinctrl-names property

The "pinctrl-names" property in iomux node does not make sense on its
own (without "pinctrl-X").
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

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

@@ -388,8 +388,6 @@ &wdog1 {
 };
 
 &iomuxc {
-	pinctrl-names = "default";
-
 	pinctrl_fec1: fec1grp {
 		fsl,pins = <
 			MX8MM_IOMUXC_ENET_MDC_ENET1_MDC			0x3