Collect them right under #ifdef CONFIG_BFQ_CGROUP_DEBUG.  The next
patch will use them from !DEBUG path and this makes it easy to move
them out of the ifdef block.

This is pure code reorganization.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>