arm64: dts: imx8m: Pass a label to the soc node

Pass a label to the 'soc' node to make it easier to reference
it from other devicetree files.

U-Boot, for example usually needs to access the AIPS node to
pass U-Boot-specific properties.
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm.dtsi

@@ -287,7 +287,7 @@ usbphynop2: usbphynop2 {
 		clock-names = "main_clk";
 	};
 
-	soc@0 {
+	soc: soc@0 {
 		compatible = "fsl,imx8mm-soc", "simple-bus";
 		#address-cells = <1>;
 		#size-cells = <1>;

arch/arm64/boot/dts/freescale/imx8mn.dtsi

@@ -269,7 +269,7 @@ timer {
 		arm,no-tick-in-suspend;
 	};
 
-	soc@0 {
+	soc: soc@0 {
 		compatible = "fsl,imx8mn-soc", "simple-bus";
 		#address-cells = <1>;
 		#size-cells = <1>;

arch/arm64/boot/dts/freescale/imx8mp.dtsi

@@ -293,7 +293,7 @@ timer {
 		arm,no-tick-in-suspend;
 	};
 
-	soc@0 {
+	soc: soc@0 {
 		compatible = "fsl,imx8mp-soc", "simple-bus";
 		#address-cells = <1>;
 		#size-cells = <1>;

arch/arm64/boot/dts/freescale/imx8mq.dtsi

@@ -320,7 +320,7 @@ timer {
 		arm,no-tick-in-suspend;
 	};
 
-	soc@0 {
+	soc: soc@0 {
 		compatible = "fsl,imx8mq-soc", "simple-bus";
 		#address-cells = <1>;
 		#size-cells = <1>;

arch/arm64/boot/dts/freescale/imx8ulp.dtsi

@@ -137,7 +137,7 @@ scmi_sensor: protocol@15 {
 		};
 	};
 
-	soc@0 {
+	soc: soc@0 {
 		compatible = "simple-bus";
 		#address-cells = <1>;
 		#size-cells = <1>;