realtek: add missing GPIO irq properties

The internal GPIO controller on RTL838x is also an IRQ controller, which
requires the 'interrupt-controller' and '#interrupts-cells' properties
to be present in the device tree.

Reported-by: INAGAKI Hiroshi <musashino.open@gmail.com>
Signed-off-by: Sander Vanheule <sander@svanheule.net>

target/linux/realtek/dts-5.10/rtl838x.dtsi

@@ -170,9 +170,13 @@
 		gpio0: gpio-controller@3500 {
 			compatible = "realtek,rtl8380-gpio", "realtek,otto-gpio";
 			reg = <0x3500 0x20>;
+
 			gpio-controller;
 			#gpio-cells = <2>;
 			ngpios = <24>;
+
+			interrupt-controller;
+			#interrupt-cells = <2>;
 			interrupt-parent = <&intc>;
 			interrupts = <23>;
 		};