csske will be removed in a future machine. Ignore it for expanding the
cpu model. Otherwise qemu falls back to z9.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: qemu-stable@nongnu.org
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-Id: <20190429090250.7648-3-borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>