Support EVP_DigestSqueeze() for in the digest provider for s390x.

Support EVP_DigestSqueeze() for in the digest provider for s390x.

The new EVP_DigestSqueeze() API requires changes to all keccak-based
digest provider implementations. Update the s390x-part of the SHA3
digest provider.

Squeeze for SHA3 is not supported, so add an empty function pointer
(NULL).

Signed-off-by: Holger Dengler <dengler@linux.ibm.com>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
Reviewed-by: Todd Short <todd.short@me.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/22221)