drm/amd/display: Improve registers write

Add REG_SEQ_SUBMIT and REG_SEQ_WAIT_DONE to optimize the burst write for
the regama lut.

Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>