qemu: introduce capability for virtual-css-bridge

qemu: introduce capability for virtual-css-bridge

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: Shalini Chellathurai Saroja <shalini@linux.vnet.ibm.com>
Reviewed-by: Bjoern Walk <bwalk@linux.ibm.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.ibm.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>