filesystems: add set_nlink()

Replace remaining direct i_nlink updates with a new set_nlink()
updater function.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

fs/bfs/dir.c

@@ -199,7 +199,7 @@ static int bfs_unlink(struct inode *dir, struct dentry *dentry)
 		printf("unlinking non-existent file %s:%lu (nlink=%d)\n",
 					inode->i_sb->s_id, inode->i_ino,
 					inode->i_nlink);
-		inode->i_nlink = 1;
+		set_nlink(inode, 1);
 	}
 	de->ino = 0;
 	mark_buffer_dirty_inode(bh, dir);