drm/amd/display: change dc stream color settings only in atomic commit

drm/amd/display: change dc stream color settings only in atomic commit

Don't update DC stream color components during atomic check. The driver
will continue validating the new CRTC color state but will not change DC
stream color components. The DC stream color state will only be
programmed at commit time in the `atomic_setup_commit` stage.

It fixes gamma LUT loss reported by KDE users when changing brightness
quickly or changing Display settings (such as overscan) with nightlight
on and HDR. As KWin can do a test commit with color settings different
from those that should be applied in a non-test-only commit, if the
driver changes DC stream color state in atomic check, this state can be
eventually HW programmed in commit tail, instead of the respective state
set by the non-blocking commit.

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4444
Reported-by: Xaver Hugl <xaver.hugl@gmail.com>
Signed-off-by: Melissa Wen <mwen@igalia.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>