drivers/vhost: Replace synchronize_rcu_bh() with synchronize_rcu()

Now that synchronize_rcu() waits for bh-disable regions of code as well
as RCU read-side critical sections, synchronize_rcu_bh() can be replaced
by synchronize_rcu().  This commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: <kvm@vger.kernel.org>
Cc: <virtualization@lists.linux-foundation.org>
Cc: <netdev@vger.kernel.org>

drivers/vhost/net.c

@@ -1359,7 +1359,7 @@ static int vhost_net_release(struct inode *inode, struct file *f)
 	if (rx_sock)
 		sockfd_put(rx_sock);
 	/* Make sure no callbacks are outstanding */
-	synchronize_rcu_bh();
+	synchronize_rcu();
 	/* We do an extra flush before freeing memory,
 	 * since jobs can re-queue themselves. */
 	vhost_net_flush(n);