block: skip unnecessary checks for split bio

block: skip unnecessary checks for split bio

Lots of checks are already done while submitting this bio the first
time, and there is no need to check them again when this bio is
resubmitted after split.

Hence open code should_fail_bio() and blk_throtl_bio() that are still
necessary from submit_bio_split_bioset().

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>