block, bfq: cleanup bfq_bfqq_to_bfqg()

Use bfq_group() instead, which do the same thing.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20220129015924.3958918-2-yukuai3@huawei.com


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