cfq-iosched: get rid of the coop_preempt flag

We need to rework this logic post the cooperating cfq_queue merging,
for now just get rid of it and Jeff Moyer will fix the fall out.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --cc block/cfq-iosched.c
Simple merge