crypto: sahara - fix cbc selftest failure

The kernel crypto API requires that all CBC implementations update the IV
buffer to contain the last ciphertext block.

This fixes the following cbc selftest error:
alg: skcipher: sahara-cbc-aes encryption test failed (wrong output IV) on
test vector 0, cfg="in-place (one sglist)"

Fixes: 5de88752 ("crypto: sahara - Add driver for SAHARA2 accelerator.")
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>