KVM: s390: consider epoch index on hotplugged CPUs

We must copy both, the epoch and the epoch_idx.

Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20180207114647.6220-4-david@redhat.com>
Fixes: 8fa1696e ("KVM: s390: Multiple Epoch Facility support")
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Fixes: 8fa1696e ("KVM: s390: Multiple Epoch Facility support")
Cc: stable@vger.kernel.org
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>