block: prohibit calls to bio_chain_endio

block: prohibit calls to bio_chain_endio

Now that all potential callers of bio_chain_endio have been
eliminated, completely prohibit any future calls to this function.

Suggested-by: Ming Lei <ming.lei@redhat.com>
Suggested-by: Andreas Gruenbacher <agruenba@redhat.com>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Shida Zhang <zhangshida@kylinos.cn>
Signed-off-by: Jens Axboe <axboe@kernel.dk>