Fix cipher reinit on s390x if no key is specified

Fix cipher reinit on s390x if no key is specified

If key==null on EVP_CipherInit_ex, the init functions for the hardware
implementation is not called.  The s390x implementation of OFB and CFB mode
used the init function to copy the IV into the hardware causing test failures
on cipher reinit.  Fix this by moving the copy operation into the cipher
operation.

Signed-off-by: Juergen Christ <jchrist@linux.ibm.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Patrick Steuer <patrick.steuer@de.ibm.com>
(Merged from https://github.com/openssl/openssl/pull/13984)