arm64: dts: alpine: Align GIC nodename with dtschema

Fix dtschema validator warnings like:
    gic@f0100000: $nodename:0:
        'gic@f0100000' does not match '^interrupt-controller(@[0-9a-f,]+)*$'

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>