block: don't declare submit_bio_checks in local header

submit_bio_checks() won't be called outside of block/blk-core.c any more
since commit 9d497e29 ("block: don't protect submit_bio_checks by
q_usage_counter"), so mark it as one local helper.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220216044514.2903784-4-ming.lei@redhat.com


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