Qemu fails with below error when trying to run with virtio pmem:

 (qemu) qemu-system-x86_64: -device virtio-pmem-pci,memdev=mem1,id=nv1:
  device is modern-only, use disable-legacy=on

 This patch fixes this by forcing virtio 1 with virtio-pmem.

fixes: adf0748a ("virtio-pci: Proxy for virtio-pmem")
Signed-off-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Message-Id: <20200925102251.7216-1-pankaj.gupta.linux@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>