virtio-ccw: remove qdev_unparent in unplug routing

This patch fixes unplugging a virtio-ccw device. We no
longer need to do that in virtio-ccw since common code does now
proper handling.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
virtio-ccw: Wire up virtio-rng.

Make virtio-rng devices available for s390-ccw-virtio machines.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>