block, bfq: avoid moving bfqq to it's parent bfqg

Moving bfqq to it's parent bfqg is pointless.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20220129015924.3958918-3-yukuai3@huawei.com


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