Adding ccw bus address support to the optional address parameter of virsh
attach-disk. The format used is ccw:cssid. ssid.devno, e.g.
ccw:0xfe.0x0.0x0201

Virtio-ccw devices must have their cssid set to 0xfe.
Signed-off-by: NStefan Zimmermann <stzi@linux.vnet.ibm.com>
Reviewed-by: NBoris Fiuczynski <fiuczy@linux.vnet.ibm.com>
Reviewed-by: NCornelia Huck <cornelia.huck@de.ibm.com>