crypto: ahash - Fix infinite recursion in ahash_def_finup

Invoke the final function directly in the default finup implementation
since crypto_ahash_final is now just a wrapper around finup.

Reported-by: Eric Biggers <ebiggers@kernel.org>
Fixes: 9d7a0ab1 ("crypto: ahash - Handle partial blocks in API")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>