jbd/jbd2: nuke write_super from comments

The '->write_super' superblock method is gone, and this patch removes all the
references to 'write_super' from various jbd and jbd2.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index e9a3c4c..8625da2 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -612,8 +612,8 @@
 		ret = 1;
 	} else if (journal->j_committing_transaction) {
 		/*
-		 * If ext3_write_super() recently started a commit, then we
-		 * have to wait for completion of that transaction
+		 * If commit has been started, then we have to wait for
+		 * completion of that transaction.
 		 */
 		if (ptid)
 			*ptid = journal->j_committing_transaction->t_tid;