dt-bindings: gpu: mali-bifrost: Set power-domains maxItems to 5

dt-bindings: gpu: mali-bifrost: Set power-domains maxItems to 5

In preparation for adding (and fixing) power-domain-names and MediaTek
MT8192 bindings, allow up to five items for power-domains.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230316102041.210269-3-angelogioacchino.delregno@collabora.com