dt-bindings: gpu: mali-bifrost: Add support for MediaTek MT8186

MT8186 has a Mali-G52 MC2 2EE GPU (two cores): add a binding with
two power domains (one per core) for it.

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/20230316102041.210269-7-angelogioacchino.delregno@collabora.com