crypto: ixp4xx - update IV after requests

Crypto selftests fail on ixp4xx since it do not update IV after skcipher
requests.

Fixes: 81bef015 ("crypto: ixp4xx - Hardware crypto support for IXP4xx CPUs")
Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>