reverts the commit
77a4229719e511a0d38d9c355317ae1469adeb54 since now we use REQ_TYPE_FS
for flush requests.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
–Sð½–