drm/nouveau/gv100-: switch to volta semaphore methods

HOPPER_CHANNEL_GPFIFO_A removes the SEMAPHORE[A-D] methods that are
currently used by nouveau to implement fences on GF100 and newer.

Switch to the newer SEM methods available from VOLTA_CHANNEL_GPFIFO,
which are also available on the Hopper/Blackwell host classes.

Signed-off-by: Ben Skeggs <bskeggs@nvidia.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Timur Tabi <ttabi@nvidia.com>
Tested-by: Timur Tabi <ttabi@nvidia.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>