CPU hotplug is only possible on a per core basis on s390x. So let's
add possible_cpus and wire everything up properly.
Signed-off-by: NDavid Hildenbrand <david@redhat.com>
Message-Id: <20170913132417.24384-19-david@redhat.com>
Acked-by: NIgor Mammedov <imammedo@redhat.com>
Signed-off-by: NCornelia Huck <cohuck@redhat.com>