Introduces the vfio-ccw model for mediated devices and prime vfio-ccw
devices such that CCW address will be generated.

Alters the qemuxml2xmltest for testing a basic mdev device using vfio-ccw.
Signed-off-by: NShalini Chellathurai Saroja <shalini@linux.vnet.ibm.com>
Reviewed-by: NBjoern Walk <bwalk@linux.ibm.com>
Reviewed-by: NBoris Fiuczynski <fiuczy@linux.ibm.com>
Reviewed-by: NMarc Hartmayer <mhartmay@linux.vnet.ibm.com>
Reviewed-by: NStefan Zimmermann <stzi@linux.ibm.com>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>