drm: Check that the plane supports the request format+modifier combo

Currently we only check that the plane supports the pixel format of the
fb we're about to feed to it. Extend it to check also the modifier, and
more specifically that the combination of the format and modifier is
supported.

Cc: dri-devel@lists.freedesktop.org
Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: Daniel Stone <daniels@collabora.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171222192231.17981-8-ville.syrjala@linux.intel.com


Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>