arm64: dts: socfpga: agilex: add unit address to soc node

The "soc" node has ranges with addresses, so it is should have unit
address  to fix dtc W=1 warnings like:

  socfpga_agilex.dtsi:152.6-674.4: Warning (unit_address_vs_reg): /soc: node has a reg or ranges property, but no unit name
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>

arch/arm64/boot/dts/intel/socfpga_agilex.dtsi

@@ -149,7 +149,7 @@ usbphy0: usbphy {
 		compatible = "usb-nop-xceiv";
 	};
 
-	soc {
+	soc@0 {
 		#address-cells = <1>;
 		#size-cells = <1>;
 		compatible = "simple-bus";

arch/arm64/boot/dts/intel/socfpga_agilex_n6000.dts

@@ -26,7 +26,7 @@ memory@80000000 {
 		reg = <0 0x80000000 0 0>;
 	};
 
-	soc {
+	soc@0 {
 		bus@80000000 {
 			compatible = "simple-bus";
 			reg = <0x80000000 0x60000000>,

arch/arm64/boot/dts/intel/socfpga_n5x_socdk.dts

@@ -25,7 +25,7 @@ memory@80000000 {
 		reg = <0 0x80000000 0 0>;
 	};
 
-	soc {
+	soc@0 {
 		sdram_edac: memory-controller@f87f8000 {
 			compatible = "snps,ddrc-3.80a";
 			reg = <0xf87f8000 0x400>;