Revert "blk-cgroup: delay blk-cgroup initialization until add_disk"

This reverts commit 178fa7d4.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230214183308.1658775-4-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>