crypto: s390/sha - replace raw value by their coresponding define

SHA_MAX_STATE_SIZE is just the number of u32 word for SHA512.
So replace the raw value "16" by their meaning (SHA512_DIGEST_SIZE / 4)

Signed-off-by: LABBE Corentin <clabbe.montjoie@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>