drm/mediatek: ovl: Add blend_modes to driver data

OVL_CON_CLRFMT_MAN is a configuration for extending color format
settings of DISP_REG_OVL_CON(n).
It will change some of the original color format settings.

Take the settings of (3 << 12) for example.
- If OVL_CON_CLRFMT_MAN = 0 means OVL_CON_CLRFMT_RGBA8888.
- If OVL_CON_CLRFMT_MAN = 1 means OVL_CON_CLRFMT_PARGB8888.

Since previous SoCs did not support OVL_CON_CLRFMT_MAN, this means
that the SoC does not support the premultiplied color format.
It will break the original color format setting of MT8173.

Therefore, the blend_modes is added to the driver data and then
mtk_ovl_fmt_convert() will check the blend_modes to see if
pre-multiplied is supported in the current platform.
If it is not supported, use coverage mode to set it to the supported
color formats to solve the degradation problem.

Fixes: a3f7f7ef ("drm/mediatek: Support "Pre-multiplied" blending in OVL")
Signed-off-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20241009034646.13143-5-jason-jh.lin@mediatek.com/


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