Cull distances are just a special case of clip distances as far as the
hardware is concerned. Make sure that the relevant "planes" are enabled,
and flip the clip mode to cull for those.
Signed-off-by: Tobias Klausmann <tobias.johannes.klausmann@mni.thm.de>
[imirkin: add enables on nvc0, add nv50 support]
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Tobias Klausmann <tobias.johannes.klausmann@mni.thm.de>