s390x: Fix Keccak implementation

s390x: Fix Keccak implementation

s390x does not directly support keccak via CPACF since these instructions
hard-code the padding to either SHA-3 or SHAKE for the "compute last message
digest" function.  This caused test errors on Keccak digests.  Fix it by using
"compute intermediate message digest" and manually computing the padding for
Keccak.

Fixes: a8b238f0e4c1 ("Fix SHA, SHAKE, and KECCAK ASM flag passing")
Signed-off-by: Juergen Christ <jchrist@linux.ibm.com>
Reviewed-by: Patrick Steuer <patrick.steuer@de.ibm.com>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18794)