block, bfq: remove bfq_log_bfqg()

It's not used, hence can be removed.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240909134154.954924-5-yukuai1@huaweicloud.com


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