drm/mediatek: Add support for AR30 and BA30 overlays

Add the ability for the Mediatek DRM driver to control
the bit depth register. If the DTS indicates the device supports
10-bit overlays and the current format has a fourcc of AR30, BA30,
or RA30, we set the bit depth register to 10 bit.

The next patch in the series actually enables 10-bit overlays for
MT8195 devices, but this current patch should be a no-op. This
patch was tested by simply running Chrome on an MT8195 and looking
for regressions.

Signed-off-by: Justin Green <greenjustin@chromium.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20230309210623.1167567-1-greenjustin@chromium.org/


Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>