drm/i915: Add a .color_post_update() hook

drm/i915: Add a .color_post_update() hook

We're going to need stuff after the color management
register latching has happened. Add a corresponding hook.

Cc: <stable@vger.kernel.org> #v5.19+
Cc: Manasi Navare <navaremanasi@google.com>
Cc: Drew Davenport <ddavenport@chromium.org>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230320095438.17328-4-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>