Let us introduce the capability QEMU_CAPS_CCW for virtual-css-bridge
and replace QEMU_CAPS_VIRTIO_CCW with QEMU_CAPS_CCW in code segments
which identify support for ccw devices.

The virtual-css-bridge is part of the ccw support introduced in QEMU 2.7.
The QEMU_CAPS_CCW capability is based on the existence of the QEMU type.

Let us also add the capability QEMU_CAPS_CCW to the tests which
require support for ccw devices.
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: NJohn Ferlan <jferlan@redhat.com>