arm64: zynqmp: Add references to cpu nodes

Add missing references to all cpu nodes.
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Moritz Fischer <mdf@kernel.org>

arch/arm64/boot/dts/xilinx/zynqmp.dtsi

@@ -20,28 +20,28 @@ cpus {
 		#address-cells = <1>;
 		#size-cells = <0>;
 
-		cpu@0 {
+		cpu0: cpu@0 {
 			compatible = "arm,cortex-a53", "arm,armv8";
 			device_type = "cpu";
 			enable-method = "psci";
 			reg = <0x0>;
 		};
 
-		cpu@1 {
+		cpu1: cpu@1 {
 			compatible = "arm,cortex-a53", "arm,armv8";
 			device_type = "cpu";
 			enable-method = "psci";
 			reg = <0x1>;
 		};
 
-		cpu@2 {
+		cpu2: cpu@2 {
 			compatible = "arm,cortex-a53", "arm,armv8";
 			device_type = "cpu";
 			enable-method = "psci";
 			reg = <0x2>;
 		};
 
-		cpu@3 {
+		cpu3: cpu@3 {
 			compatible = "arm,cortex-a53", "arm,armv8";
 			device_type = "cpu";
 			enable-method = "psci";