drm/i915: Fix VLV color state readout

VLV was missed when the color.get_config() hook was added.
Remedy that.

Not really sure what the final plan here was since a bunch of
color related readout was left in intel_display.c anyway,
but that's for anothr day to figure out...

Cc: Jani Nikula <jani.nikula@intel.com>
Fixes: 9af09dfc ("drm/i915/color: move pre-SKL gamma and CSC enable read to intel_color")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231009145828.12960-1-ville.syrjala@linux.intel.com


Reviewed-by: Jani Nikula <jani.nikula@intel.com>