drm/amd/display: For new fast update path, loop through each surface

drm/amd/display: For new fast update path, loop through each surface

[Description]
- Previous implementation didn't consider multiple surfaces in a flip
- Loop through each surface in each flip to ensure the update path is
  correct

Reviewed-by: Samson Tam <samson.tam@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>