drm/nouveau/gr/gp10b: Use gp100_grctx and gp100_gr_zbc

gp10b doesn't have all the registers that gp102_gr_zbc wants to access,
which causes IBUS MMIO faults to occur. Avoid this by using the gp100
variants of grctx and gr_zbc.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>