dt-bindings: gpu: mali-bifrost: Add sub-schema for MT8192's power domains

MediaTek MT8192 (and similar) needs five power domains for the
Mali GPU and no sram-supply: change the binding to allow so by
also introducing power-domain-names in the generic binding;
while at it, also disallow the newly introduced power-domain-names
for all non-MediaTek bindings.

Fixes: 5d82e74a ("dt-bindings: Add compatible for Mali Valhall (JM)")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230316102041.210269-5-angelogioacchino.delregno@collabora.com