arm64: dts: uniphier: add pinctrl property to System Bus node

This pinctrl is needed to get access to the UniPhier System Bus.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

arch/arm64/boot/dts/socionext/uniphier-ld20.dtsi

@@ -260,6 +260,8 @@ system_bus: system-bus@58c00000 {
 			reg = <0x58c00000 0x400>;
 			#address-cells = <2>;
 			#size-cells = <1>;
+			pinctrl-names = "default";
+			pinctrl-0 = <&pinctrl_system_bus>;
 		};
 
 		smpctrl@59800000 {