s390x: Fix prehash-by-caller handling for ED25519 and ED448

In case of prehash or prehash-by-caller is set skip the s390x specific
acceleration an fallback to the non-accelerated code path.

Fixes: 66966827

Signed-off-by: Ingo Franzki <ifranzki@linux.ibm.com>

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/25351)