[PATCH] reiserfs_fsync should only use barriers when they are enabled

make sure that reiserfs_fsync only triggers barriers when mounted with -o
barrier=flush

Signed-off-by: Chris Mason <mason@suse.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>