As a preparation for wiring-up virtio-crypto, the first non-transitional
virtio device on the ccw transport, let us introduce a mechanism for
disabling revision 0. This is more or less equivalent with disabling
legacy as revision 0 is legacy only, and legacy drivers use the revision
0 exclusively.
Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>