vdpa: manual forward CVQ buffers Do a simple forwarding of CVQ buffers, the same work SVQ could do but through callbacks. No functional change intended. Signed-off-by: Eugenio Pérez <eperezma@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Jason Wang <jasowang@redhat.com>