drm/mediatek: Add plane check in async_check function

MTK do rotation checking and transferring in layer check function,
but we do not check that in atomic_check,
so add back in atomic_check function.

Fixes: 920fffcc

 ("drm/mediatek: update cursors by using async atomic update")

Signed-off-by: Bibby Hsieh <bibby.hsieh@mediatek.com>
Signed-off-by: CK Hu <ck.hu@mediatek.com>