[openssl/openssl] ed37a8: s390x: fix ecx derive

[Juergen Christ]

  Branch: refs/heads/openssl-3.0
  Home:   https://github.com/openssl/openssl
  Commit: ed37a881f450a07520084f4cd8bfaed294d31141
      https://github.com/openssl/openssl/commit/ed37a881f450a07520084f4cd8bfaed294d31141
  Author: Juergen Christ <jchrist at linux.ibm.com>
  Date:   2022-09-09 (Fri, 09 Sep 2022)

  Changed paths:
    M crypto/ec/ecx_meth.c

  Log Message:
  -----------
  s390x: fix ecx derive

Derivation via ecx-methods did not properly set the length.  Make the code
more similar to common code and set the length property.

Signed-off-by: Juergen Christ <jchrist at linux.ibm.com>

Reviewed-by: Tomas Mraz <tomas at openssl.org>
Reviewed-by: Paul Dale <pauli at openssl.org>
Reviewed-by: Hugo Landau <hlandau at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19158)

(cherry picked from commit 3cca05cc194c0528865deea57d9e60ca3fb0e5d3)