reiserfs: use per-fs commit workqueues

The reiserfs write lock hasn't been the BKL for some time. There's no
need to have different file systems queued up on the same workqueue.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --cc fs/reiserfs/journal.c
Simple merge

diff --cc fs/reiserfs/reiserfs.h
Simple merge

diff --cc fs/reiserfs/super.c
Simple merge