drm/i915: Expose 10:10:10 XRGB formats on SNB-BDW sprites

SNB-BDW support 10:10:10 formats on the sprite planes. Let's expose
them.

v2: Rebase due to fp16 landing

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/20191031165652.10868-2-ville.syrjala@linux.intel.com