block, bfq: Reorder struct bfq_iocq_bfqq_data

The size of struct bfq_iocq_bfqq_data can be reduced by moving a few
fields around.

On a x86_64, with allmodconfig, this shrinks the size from 144 to 128
bytes. The main benefit is to reduce the size of struct bfq_io_cq from
1360 to 1232.

This structure is stored in a dedicated slab cache. So reducing its size
improves cache usage.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/79394db1befaa658e8066b8e3348073ce27d9d26.1754119538.git.christophe.jaillet@wanadoo.fr


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