drm/mediatek: Add new color format MACROs in OVL

Define new color formats to hide the bit operation in the MACROs to make
the switch statement more concise.
Change the MACROs to align the naming rule in DRM.

Reviewed-by: CK Hu <ck.hu@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Hsiao Chien Sung <shawn.sung@mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20240620-igt-v3-9-a9d62d2e2c7e@mediatek.com/


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