drm/mediatek: use DRM core's atomic commit helper

The DRM core atomic helper now supports asynchronous commits natively.
The custom drm implementation isn't needed anymore, remove it.

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