ARM: dts: uniphier: fix no unit name warnings

Fix warnings reported when built with W=1, by DTC 1.4.2 or later:
  Node /memory has a reg or ranges property, but no unit name

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/arch/arm/dts/uniphier-pxs3.dtsi b/arch/arm/dts/uniphier-pxs3.dtsi
index 3b30eef..76b6566 100644
--- a/arch/arm/dts/uniphier-pxs3.dtsi
+++ b/arch/arm/dts/uniphier-pxs3.dtsi
@@ -86,7 +86,7 @@
 			     <1 10 4>;
 	};
 
-	soc {
+	soc@0 {
 		compatible = "simple-bus";
 		#address-cells = <1>;
 		#size-cells = <1>;