crypto: crypto4xx - Switch to new style ahash

This patch changes crypto4xx to use the new style ahash type.
In particular, we now use ahash_alg to define ahash algorithms
instead of crypto_alg.

This is achieved by introducing a union that encapsulates the
new type and the existing crypto_alg structure.  They're told
apart through a u32 field containing the type value.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>