filesystems: add missing nlink wrappers

Replace direct i_nlink updates with the respective updater function
(inc_nlink, drop_nlink, clear_nlink, inode_dec_link_count).

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

fs/ext3/namei.c

@@ -1833,7 +1833,7 @@ retry:
 
 	if (err) {
 out_clear_inode:
-		inode->i_nlink = 0;
+		clear_nlink(inode);
 		unlock_new_inode(inode);
 		ext3_mark_inode_dirty(handle, inode);
 		iput (inode);