drm/i915/chv: Update csc coefficient matrix during modeset

During modeset, previously configured csc coefficient matrix,if any, will
not persist. This can result in blank screen as csc mode will be programmed
while loading LUT but csc coefficient matrix remains unprogrammed.

Changes since V1:
- Removed platform check

Signed-off-by: P Raviraj Sitaram <raviraj.p.sitaram@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1536589634-29680-1-git-send-email-raviraj.p.sitaram@intel.com