[why]
There is only a single call to dc_post_update_surfaces_to_stream
so there is no need to have two flags to control it. Unifying
this to a single flag allows dc_stream_adjust_vmin_vmax to skip
actual programming when there is no change required.

[how]
Remove wm_optimze_required flag and set only optimize_required in its
place.  Then in dc_stream_adjust_vmin_vmax, check that the stream timing
range matches the requested one and skip programming if they are equal.
Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Aric Cyr <aric.cyr@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>