virtio: fix 1.0 virtqueue migration

virtio: fix 1.0 virtqueue migration

1.0 does not requires physically-contiguous pages layout for a
virtqueue. So we could not infer avail and used from desc. This means
we need to migrate vring.avail and vring.used when host support virtio
1.0. This fixes malfunction of virtio 1.0 device after migration.

Cc: Michael S. Tsirkin <[email protected]>
Cc: Cornelia Huck <[email protected]>
Cc: Dr. David Alan Gilbert <[email protected]>
Signed-off-by: Jason Wang <[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>