ARM64: zynqmp: DT: Add interrupt-controller property to GPIO

GPIO can be used as interrupt-controller. Add the missing properties to
the GPIO node.
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/arm64/boot/dts/xilinx/zynqmp.dtsi

@@ -133,6 +133,8 @@ gpio: gpio@ff0a0000 {
 			clocks = <&misc_clk>;
 			interrupt-parent = <&gic>;
 			interrupts = <0 16 4>;
+			interrupt-controller;
+			#interrupt-cells = <2>;
 			reg = <0x0 0xff0a0000 0x1000>;
 		};