s390x assembly pack: remove chacha20 dependency on non-base memnonics

Signed-off-by: Patrick Steuer <patrick.steuer@de.ibm.com>

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8181)