All the different virtio ccw devices use the same reset handler,
so let's move setting it into the base virtio ccw device class.

CC: qemu-stable@nongnu.org
Reviewed-by: NThomas Huth <thuth@redhat.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Reviewed-by: NHalil Pasic <pasic@linux.ibm.com>
Signed-off-by: NCornelia Huck <cohuck@redhat.com>