ARM: dts: ls1021a: fix memory node for schema check

Fix the following error from "make dtbs_check"

memory: False schema does not allow ...
Signed-off-by: Li Yang <leoyang.li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/ls1021a.dtsi

@@ -47,7 +47,7 @@ cpu1: cpu@f01 {
 		};
 	};
 
-	memory {
+	memory@0 {
 		device_type = "memory";
 		reg = <0x0 0x0 0x0 0x0>;
 	};