ARM: dts: imx51: Fix sram.yaml warnings

Add ranges, #address-cells and #size-cells properties to the sram
node to fix the following warnings when checking sram.yaml:

make dtbs_check DT_SCHEMA_FILES=sram.yaml
...
arch/arm/boot/dts/imx51-apf51.dtb: sram@1ffe0000: '#address-cells' is a required property
	From schema: Documentation/devicetree/bindings/sram/sram.yaml
arch/arm/boot/dts/imx51-apf51.dtb: sram@1ffe0000: '#size-cells' is a required property
	From schema: Documentation/devicetree/bindings/sram/sram.yaml
arch/arm/boot/dts/imx51-apf51.dtb: sram@1ffe0000: 'ranges' is a required property
	From schema: Documentation/devicetree/bindings/sram/sram.yaml
Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx51.dtsi

@@ -124,6 +124,9 @@ soc: soc {
 		iram: sram@1ffe0000 {
 			compatible = "mmio-sram";
 			reg = <0x1ffe0000 0x20000>;
+			ranges = <0 0x1ffe0000 0x20000>;
+			#address-cells = <1>;
+			#size-cells = <1>;
 		};
 
 		gpu: gpu@30000000 {