nilfs2: nuke write_super from comments

The '->write_super' superblock method is gone, and this patch removes all the
references to 'write_super' from ntfs.

Cc: KONISHI Ryusuke <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/nilfs2/the_nilfs.h

@@ -107,8 +107,6 @@ struct the_nilfs {
 	 * used for
 	 * - loading the latest checkpoint exclusively.
 	 * - allocating a new full segment.
-	 * - protecting s_dirt in the super_block struct
-	 *   (see nilfs_write_super) and the following fields.
 	 */
 	struct buffer_head     *ns_sbh[2];
 	struct nilfs_super_block *ns_sbp[2];