cfq-iosched: move IO controller declerations to a header file

They should not be declared inside some other file that's not related
to CFQ.

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

diff --cc block/blk-cgroup.c
Simple merge

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

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