drm/amd/display: Modify power sequence

Need to update the power sequence to help prevent potential issues
like multi-display or multi-plane.

Reviewed-by: Duncan Ma <duncan.ma@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Sung Joon Kim <sungjoon.kim@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>