Throttled bios can't be issued after del_gendisk() is done, thus
it's better to cancel them immediately rather than waiting for
throttle is done.

For example, if user thread is throttled with low bps while it's
issuing large io, and the device is deleted. The user thread will
wait for a long time for io to return.
Signed-off-by: NYu Kuai <yukuai3@huawei.com>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220318130144.1066064-4-ming.lei@redhat.comSigned-off-by: NJens Axboe <axboe@kernel.dk>