drm/mediatek: Add mdp_rdma get format function

Add mdp_rdma get_format and get_num_formats function.

Signed-off-by: Nancy.Lin <nancy.lin@mediatek.com>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20230330032614.18837-2-nancy.lin@mediatek.com/


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