drm/i915: add missing condition for committing planes on crtc

The i915 driver checks for color management properties changes as part
of a plane update. Therefore a color management update must imply a
plane update, otherwise we never update the transformation matrixes
and degamma/gamma LUTs.

v2: add comment about moving the commit of color management registers
    to an async worker

v3: Commit color management register right after vblank

v4: Move back color management commit condition together with planes
    commit

v5: Trigger color management commit through the planes commit (Daniel)

v6: Make plane change update more readable

Fixes: 20a34e78 (drm/i915: Update color management during vblank evasion.)
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: drm-intel-fixes@lists.freedesktop.org
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
References: https://lkml.org/lkml/2016/7/14/614


Reviewed-and-tested-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1464183041-8478-1-git-send-email-lionel.g.landwerlin@intel.com