drm/i915: Make sure CCS YUV semiplanar format checks work

For CCS formats, the current DRM core check for YUV semiplanar formats
doesn't work; use an i915 specific function for that.

v2: Fix checkpatch warnings.

Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191221120543.22816-11-imre.deak@intel.com