We used to have a per device feature whitelist to filter out the
unsupported virtio features. But this seems unnecessary since:

- the main idea behind feature whitelist is to block control vq
  feature until we finalize the control virtqueue API. But the current
  vhost-vDPA uAPI is sufficient to support control virtqueue. For
  device that has hardware control virtqueue, the vDPA device driver
  can just setup the hardware virtqueue and let userspace to use
  hardware virtqueue directly. For device that doesn't have a control
  virtqueue, the vDPA device driver need to use e.g vringh to emulate
  a software control virtqueue.
- we don't do it in virtio-vDPA driver

So remove this limitation.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20200720085043.16485-1-jasowang@redhat.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>