After the previous patch to cfq, there's no ioc_get_changed() user
left.  This patch yanks out ioc_{ioprio|cgroup|get}_changed() and all
related stuff.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>