vhost-scsi: remove incorrect memory barrier

At this point, vs_tpg is not public at all; tv_tpg_vhost_count
is accessed under tpg->tv_tpg_mutex; tpg->vhost_scsi is
accessed under vhost_scsi_mutex.  Therefor there are no atomic
operations involved at all here, just remove the barrier.
Reported-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

drivers/vhost/scsi.c

@@ -1443,7 +1443,6 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs,
 			tpg->tv_tpg_vhost_count++;
 			tpg->vhost_scsi = vs;
 			vs_tpg[tpg->tport_tpgt] = tpg;
-			smp_mb__after_atomic();
 			match = true;
 		}
 		mutex_unlock(&tpg->tv_tpg_mutex);