drm/i915: Adjust LUT rounding rules

drm_color_lut_extract() rounding was changed to follow the
OpenGL int<->float conversion rules. Adjust intel_color_lut_pack()
to match.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231013131402.24072-3-ville.syrjala@linux.intel.com


Reviewed-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>