arm64: dts: broadcom: bcm2712: Add default GIC address cells

Add missing address-cells 0 to GIC interrupt node to silence W=1
warning:

  bcm2712.dtsi:494.4-497.31: Warning (interrupt_map): /axi/pcie@1000110000:interrupt-map:
    Missing property '#address-cells' in node /soc@107c000000/interrupt-controller@7fff9000, using 0 as fallback

Value '0' is correct because:
1. GIC interrupt controller does not have children,
2. interrupt-map property (in PCI node) consists of five components and
   the fourth component "parent unit address", which size is defined by
   '#address-cells' of the node pointed to by the interrupt-parent
   component, is not used (=0)

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250822133407.312505-2-krzysztof.kozlowski@linaro.org
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>

arch/arm64/boot/dts/broadcom/bcm2712.dtsi

@@ -270,6 +270,7 @@ gicv2: interrupt-controller@7fff9000 {
 			      <0x7fffc000 0x2000>,
 			      <0x7fffe000 0x2000>;
 			interrupt-controller;
+			#address-cells = <0>;
 			#interrupt-cells = <3>;
 		};