dm-crypt: remove clone_init

Just open code it next to the bio allocations, which saves a few lines
of code, prepares for future changes and allows to remove the duplicate
bi_opf assignment for the bio_clone_fast case in kcryptd_io_read.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220124091107.642561-7-hch@lst.de


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