ARM: zynq: Remove DTC 1.4.2 warnings

DTC 1.4.2 reports these warnings:
Warning (unit_address_vs_reg): Node /memory has a reg or ranges
property, but no unit name
Warning (unit_address_vs_reg): Node /pmu has a reg or ranges property,
but no unit name
Warning (unit_address_vs_reg): Node /fixedregulator@0 has a unit name,
but no reg property

This patch is fixing them.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/arch/arm/dts/zynq-zc770-xm012.dts b/arch/arm/dts/zynq-zc770-xm012.dts
index 6cab832..699cd2c 100644
--- a/arch/arm/dts/zynq-zc770-xm012.dts
+++ b/arch/arm/dts/zynq-zc770-xm012.dts
@@ -24,7 +24,7 @@
 		stdout-path = "serial0:115200n8";
 	};
 
-	memory {
+	memory@0 {
 		device_type = "memory";
 		reg = <0x0 0x40000000>;
 	};