ARM: dts: imx50: Add src node interrupt

Interrupt is a required property according to SRC binding, add
it for SRC node.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx50.dtsi

@@ -331,6 +331,7 @@ uart2: serial@53fc0000 {
 			src: src@53fd0000 {
 				compatible = "fsl,imx50-src", "fsl,imx51-src";
 				reg = <0x53fd0000 0x4000>;
+				interrupts = <75>;
 				#reset-cells = <1>;
 			};