drm/i915/dsb: Re-instate DSB for LUT updates

With all the known issues sorted out we can start to use
DSB to load the LUTs.

Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231009132204.15098-3-ville.syrjala@linux.intel.com