drm/i915: Deconfuse the ilk+ 12.4 LUT entry functions

s/icl_lut_multi_seg_pack/ilk_lut_12p4_pack/ since that's what it is
and group the corresponding "unpack" functions next to it.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221026113906.10551-7-ville.syrjala@linux.intel.com


Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>