drm: Add drm_format_{horz, vert}_chroma_subsampling() utility functions

These functions return the chroma subsampling factors for the specified
pixel format.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
2 files changed