drm/amd/display: Fix performance regression from full updates

drm/amd/display: Fix performance regression from full updates

[Why]
full_update_required is too strict at update_planes_and_stream_state,
causing a performance regression due to too many updates being full.

[How]
* Carve out weak version of full_update_required for use inside
update_planes_and_stream_state.

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Dominik Kaszewski <dominik.kaszewski@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>