drm/i915: Add 10bpc formats with alpha for icl+

ICL+ again supports alpha blending with 10bpc pixel formats.
Expose them.

v2: Add all the stuff I missed earlier!

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191031165652.10868-6-ville.syrjala@linux.intel.com