ARM: zynq: 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>
Reviewed-by: Moritz Fischer <moritz.fischer@ettus.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/arm/boot/dts/zynq-7000.dtsi

@@ -101,6 +101,8 @@ gpio0: gpio@e000a000 {
 			#gpio-cells = <2>;
 			clocks = <&clkc 42>;
 			gpio-controller;
+			interrupt-controller;
+			#interrupt-cells = <2>;
 			interrupt-parent = <&intc>;
 			interrupts = <0 20 4>;
 			reg = <0xe000a000 0x1000>;