blk-crypto: remove blk_crypto_insert_cloned_request()

blk_crypto_insert_cloned_request() is the same as
blk_crypto_rq_get_keyslot(), so just use that directly.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230315183907.53675-2-ebiggers@kernel.org


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