nvc0: do not break 3D state by pushing MS coordinates on Fermi

nvc0: do not break 3D state by pushing MS coordinates on Fermi

Long story short, 3D and CP are aliased on Fermi and initializing
compute after pushing the MS sample coordinate offsets seems to
corrupt 3D state for weird reasons.

I still don't have the faintest clue what is going on, but
this seems to only affect Fermi generation. A possible fix
could be to use two different channels, one for 3D and one
for CP.

This fixes a bunch of regressions pinpointed by piglit.

Fixes: "nvc0: fix up image support for allowing multiple samples"
Cc: "13.0" <mesa-stable@lists.freedesktop.org>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>