afs: Remove erroneous fallthough annotation

The fall through annotation comes after a return statement so it's not
reachable.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

fs/afs/flock.c

@@ -376,7 +376,6 @@ void afs_lock_work(struct work_struct *work)
 		spin_unlock(&vnode->lock);
 		return;
 
-		fallthrough;
 	default:
 		/* Looks like a lock request was withdrawn. */
 		spin_unlock(&vnode->lock);