ARM: dts: uniphier: drop u-boot, dm-pre-reloc from system-bus pinctrl node

Since commit 26b09c02 ("ARM: uniphier: move SBC and Support Card
init code to U-Boot proper"), SPL does not need pin-mux settings for
the System Bus.

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

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

@@ -71,7 +71,3 @@
 &pinctrl_uart0 {
 	u-boot,dm-pre-reloc;
 };
-
-&pinctrl_system_bus {
-	u-boot,dm-pre-reloc;
-};

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

@@ -59,7 +59,3 @@
 &pinctrl_uart0 {
 	u-boot,dm-pre-reloc;
 };
-
-&pinctrl_system_bus {
-	u-boot,dm-pre-reloc;
-};