block: remove redundant explicit memory barrier from rq_qos waiter and waker

The memory barriers in list_del_init_careful() and list_empty_careful()
in pairs already handle the proper ordering between data.got_token
and data.wq.entry. So remove the redundant explicit barriers. And also
change a "break" statement to "return" to avoid redundant calling of
finish_wait().

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Link: https://lore.kernel.org/r/20241021085251.73353-1-songmuchun@bytedance.com


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