arm64: dts: renesas: r8a77965: Add #interrupt-cells property

Add "#interrupt-cells" property and "interrupt-controller" label to
"interrupt-controller@e61c0000" device node.

This silences the following DTC compiler warnings:
Warning (interrupts_property): Missing interrupt-controller or
interrupt-map property in /soc/interrupt-controller@e61c0000
Warning (interrupts_property): Missing #interrupt-cells in
interrupt-parent /soc/interrupt-controller@e61c000
Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/r8a77965.dtsi

@@ -316,6 +316,8 @@ gpio7: gpio@e6055800 {
 		};
 
 		intc_ex: interrupt-controller@e61c0000 {
+			#interrupt-cells = <2>;
+			interrupt-controller;
 			reg = <0 0xe61c0000 0 0x200>;
 			/* placeholder */
 		};