ARM: dts: keystone*: Use a single soc0 instance

Provide a soc0 node and reference the same to simplify dts. This also
resolves the following warnings when built with W=1:
arch/arm/boot/dts/keystone-k2hk-evm.dtb: Warning (unit_address_vs_reg): Node /soc has a reg or ranges property, but no unit name
arch/arm/boot/dts/keystone-k2l-evm.dtb: Warning (unit_address_vs_reg): Node /soc has a reg or ranges property, but no unit name
arch/arm/boot/dts/keystone-k2e-evm.dtb: Warning (unit_address_vs_reg): Node /soc has a reg or ranges property, but no unit name
arch/arm/boot/dts/keystone-k2g-evm.dtb: Warning (unit_address_vs_reg): Node /soc has a reg or ranges property, but no unit name
arch/arm/boot/dts/keystone-k2g-ice.dtb: Warning (unit_address_vs_reg): Node /soc has a reg or ranges property, but no unit name

NOTE: Though we can reformat files by reducing 1 level of indent due to
the use of soc0 phandle, we omit that change to prevent un-necessary
churn in code base.

Reported-by: Rob Herring <[e-mail]>
Signed-off-by: Nishanth Menon <[e-mail]>
Signed-off-by: Santosh Shilimkar <[e-mail]>

arch/arm/boot/dts/keystone-k2e-evm.dts

···
 			status = "okay";
 		};
 	};
+};
 
-	soc {
+&soc0 {
 
 		clocks {
 			refclksys: refclksys {
···
 				clock-output-names = "refclk-ddr3a";
 			};
 		};
-	};
 };
 
 &usb_phy {

arch/arm/boot/dts/keystone-k2e.dtsi

···
 	aliases {
 		rproc0 = &dsp0;
 	};
+};
 
-	soc {
+&soc0 {
 		/include/ "keystone-k2e-clocks.dtsi"
 
 		usb: usb@2680000 {
···
 			bus_freq	= <2500000>;
 		};
 		/include/ "keystone-k2e-netcp.dtsi"
-	};
 };

arch/arm/boot/dts/keystone-k2g.dtsi

···
 		interrupts = <GIC_SPI 4 IRQ_TYPE_EDGE_RISING>;
 	};
 
-	soc {
+	soc0: soc@0 {
 		#address-cells = <1>;
 		#size-cells = <1>;
 		#pinctrl-cells = <1>;

arch/arm/boot/dts/keystone-k2hk-evm.dts

···
 		};
 	};
 
-	soc {
+	leds {
+		compatible = "gpio-leds";
+		debug1_1 {
+			label = "keystone:green:debug1";
+			gpios = <&gpio0 12 GPIO_ACTIVE_HIGH>; /* 12 */
+		};
+
+		debug1_2 {
+			label = "keystone:red:debug1";
+			gpios = <&gpio0 13 GPIO_ACTIVE_HIGH>; /* 13 */
+		};
+
+		debug2 {
+			label = "keystone:blue:debug2";
+			gpios = <&gpio0 14 GPIO_ACTIVE_HIGH>; /* 14 */
+		};
+
+		debug3 {
+			label = "keystone:blue:debug3";
+			gpios = <&gpio0 15 GPIO_ACTIVE_HIGH>; /* 15 */
+		};
+	};
+};
+
+&soc0 {
 		clocks {
 			refclksys: refclksys {
 				#clock-cells = <0>;
···
 				clock-output-names = "refclk-ddr3b";
 			};
 		};
-	};
-
-	leds {
-		compatible = "gpio-leds";
-		debug1_1 {
-			label = "keystone:green:debug1";
-			gpios = <&gpio0 12 GPIO_ACTIVE_HIGH>; /* 12 */
-		};
-
-		debug1_2 {
-			label = "keystone:red:debug1";
-			gpios = <&gpio0 13 GPIO_ACTIVE_HIGH>; /* 13 */
-		};
-
-		debug2 {
-			label = "keystone:blue:debug2";
-			gpios = <&gpio0 14 GPIO_ACTIVE_HIGH>; /* 14 */
-		};
-
-		debug3 {
-			label = "keystone:blue:debug3";
-			gpios = <&gpio0 15 GPIO_ACTIVE_HIGH>; /* 15 */
-		};
-	};
 };
 
 &usb_phy {

arch/arm/boot/dts/keystone-k2hk.dtsi

···
 		rproc6 = &dsp6;
 		rproc7 = &dsp7;
 	};
+};
 
-	soc {
+&soc0 {
 		/include/ "keystone-k2hk-clocks.dtsi"
 
 		msm_ram: msmram@c000000 {
···
 			bus_freq	= <2500000>;
 		};
 		/include/ "keystone-k2hk-netcp.dtsi"
-	};
 };

arch/arm/boot/dts/keystone-k2l-evm.dts

···
 			status = "okay";
 		};
 	};
+};
 
-	soc {
+&soc0 {
 		clocks {
 			refclksys: refclksys {
 				#clock-cells = <0>;
···
 				clock-output-names = "refclk-sys";
 			};
 		};
-	};
 };
 
 &usb_phy {

arch/arm/boot/dts/keystone-k2l.dtsi

···
 		rproc2 = &dsp2;
 		rproc3 = &dsp3;
 	};
+};
 
-	soc {
+&soc0 {
 		/include/ "keystone-k2l-clocks.dtsi"
 
 		uart2: serial@2348400 {
···
 			bus_freq	= <2500000>;
 		};
 		/include/ "keystone-k2l-netcp.dtsi"
-	};
 };
 
 &spi0 {

arch/arm/boot/dts/keystone.dtsi

···
 		cpu_on		= <0x84000003>;
 	};
 
-	soc {
+	soc0: soc@0 {
 		#address-cells = <1>;
 		#size-cells = <1>;
 		compatible = "ti,keystone","simple-bus";