fs/fs-writeback.c: cleanup riteback_sb_inodes kerneldoc

Argument @only_this_sb has been removed.

Signed-off-by: Liu Bo <liub.liubo@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 8f660dd..3451d37 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -582,10 +582,6 @@
 /*
  * Write a portion of b_io inodes which belong to @sb.
  *
- * If @only_this_sb is true, then find and write all such
- * inodes. Otherwise write only ones which go sequentially
- * in reverse order.
- *
  * Return the number of pages and/or inodes written.
  */
 static long writeback_sb_inodes(struct super_block *sb,