locks: missing unlock on error in generic_add_lease()

We should unlock here before returning.

Fixes: df4e8d2c1d2b ('locks: implement delegations')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/locks.c

@@ -1494,6 +1494,7 @@ static int generic_add_lease(struct file *filp, long arg, struct file_lock **flp
 
 	if (is_deleg && arg == F_WRLCK) {
 		/* Write delegations are not currently supported: */
+		mutex_unlock(&inode->i_mutex);
 		WARN_ON_ONCE(1);
 		return -EINVAL;
 	}