ARM: dts: uniphier: include System Bus pin group node in SPL DT

This will be needed for setting up the System Bus pin-mux via the
LD11/LD20 pinctrl driver.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

arch/arm/dts/uniphier-ph1-ld11-ref.dts

@@ -70,3 +70,7 @@
 &pinctrl_uart0 {
 	u-boot,dm-pre-reloc;
 };
+
+&pinctrl_system_bus {
+	u-boot,dm-pre-reloc;
+};

arch/arm/dts/uniphier-ph1-ld20-ref.dts

@@ -58,3 +58,7 @@
 &pinctrl_uart0 {
 	u-boot,dm-pre-reloc;
 };
+
+&pinctrl_system_bus {
+	u-boot,dm-pre-reloc;
+};