This patch adds two block cipher algorithms, CBC and ECB.  These
are implemented as templates on top of existing single-block cipher
algorithms.  They invoke the single-block cipher through the new
encrypt_one/decrypt_one interface.

This also optimises the in-place encryption and decryption to remove
the cost of an IV copy each round.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>