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/ext2/ialloc.c

@@ -601,7 +601,7 @@ fail_free_drop:
 fail_drop:
 	dquot_drop(inode);
 	inode->i_flags |= S_NOQUOTA;
-	inode->i_nlink = 0;
+	clear_nlink(inode);
 	unlock_new_inode(inode);
 	iput(inode);
 	return ERR_PTR(err);