arm64: dts: imx8mp: Add default GIC address cells

arm64: dts: imx8mp: Add default GIC address cells

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

  imx8mp.dtsi:2184.4-2187.29: Warning (interrupt_map): /soc@0/pcie@33800000:interrupt-map:
    Missing property '#address-cells' in node /soc@0/interrupt-controller@38800000, 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>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>