blk-cgroup: simplify blkg freeing from initialization failure paths

There is no need to delay freeing a blkg to a workqueue when freeing it
after an initialization failure.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20230203150400.3199230-5-hch@lst.de


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