dm: fold __send_duplicate_bios into __clone_and_map_simple_bio

Fold __send_duplicate_bios into its only caller to prepare for
refactoring.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Link: https://lore.kernel.org/r/20220202160109.108149-5-hch@lst.de


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