nvc0: fix 3d images on kepler

Looks like SUBFM.3D and SUEAU are perfectly capable of dealing with 3d
tiling, they just need the correct inputs. Supply them.

We also have to deal with the case where a 2d "layer" of a 3d image is
bound. In this case, we supply the z coordinate separately to the
shader, which has to optionally treat every 2d case as if it could be a
slice of a 3d texture.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: 19.0 <mesa-stable@lists.freedesktop.org>
(cherry picked from commit 162352e6)