jbd: clean up journal_try_to_free_buffers()

I delete the following patch
"commit 3f31fddf
Author: Mingming Cao <cmm@us.ibm.com>
Date:   Fri Jul 25 01:46:22 2008 -0700

    jbd: fix race between free buffer and commit transaction

This patch is no longer needed because if race between freeing buffer and
committing transaction functionality occurs and dio gets error, currently
dio falls back to buffered IO by the following patch.

	commit 6ccfa806
	Author: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
	Date:   Tue Sep 2 14:35:40 2008 -0700

   	VFS: fix dio write returning EIO when try_to_release_page fails

Signed-off-by: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
Cc: Theodore Tso <tytso@mit.edu>
Cc: Mingming Cao <cmm@us.ibm.com>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>