drm/amd/display: Query for update plane type.

Use DC interface to query for plane update type
so in case of FULL update you flush any outstanding
commits.

Signed-off-by: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>