blk-throttle: Rename tg_may_dispatch() to tg_dispatch_time()

blk-throttle: Rename tg_may_dispatch() to tg_dispatch_time()

tg_may_dispatch() can directly indicate whether bio can be dispatched by
returning the time to wait, without the need for the redundant "wait"
parameter. Remove it and modify the function's return type accordingly.

Since we have determined by the return time whether bio can be dispatched,
rename tg_may_dispatch() to tg_dispatch_time().

Signed-off-by: Zizhi Wo <wozizhi@huawei.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Zizhi Wo <wozizhi@huaweicloud.com>
Link: https://lore.kernel.org/r/20250506020935.655574-2-wozizhi@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>