drm/i915/skl+: Add YUV pixel format in Capability list

GEN >= 9 supports YUV format for all planes, but it's not exported in
Capability list of primary plane. Add YUV formats in skl_primary_formats
list.

Testcase: igt/kms_universal_plane.c

Signed-off-by: Kumar, Mahesh <mahesh1.kumar@intel.com>
Cc: Konduru, Chandra <chandra.konduru@intel.com>
Reviewed-by: Sonika Jindal <sonika.jindal@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>