riscv: dts: microchip: drop unused pinctrl-names

pinctrl-names without pinctrl-0 does not have any sense:

  arch/riscv/boot/dts/microchip/microchip-mpfs-icicle-kit.dt.yaml: sdhc@20008000: 'pinctrl-0' is a dependency of 'pinctrl-names'
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi

@@ -268,7 +268,6 @@ mmc: mmc@20008000 {
 			reg = <0x0 0x20008000 0x0 0x1000>;
 			interrupt-parent = <&plic>;
 			interrupts = <88 89>;
-			pinctrl-names = "default";
 			clocks = <&clkcfg 6>;
 			max-frequency = <200000000>;
 			status = "disabled";