block, bfq: use bfq_reassign_last_bfqq() in bfq_bfqq_move()

Instead of open coding it, there are no functional changes.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240902130329.3787024-5-yukuai1@huaweicloud.com


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