We want to get rid of plane->crtc on atomic drivers. Stop looking at it.

Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180405151400.11326-3-ville.syrjala@linux.intel.comReviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>