qemu: Introduce capabilities for virtio input ccw devices
    
    QEMU on S390 (since v2.11) can support virtio input ccw devices.
    Introduce qemu capabilities for these devices.
    
    Signed-off-by: Farhan Ali <alifm@linux.vnet.ibm.com>
    Signed-off-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>