virtio_pci: free up vq->priv

We don't need to go from vq to vq info on
data path, so using direct vq->priv pointer for that
seems like a waste.

Let's build an array of vq infos, then we can use vq->index
for that lookup.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --cc drivers/virtio/virtio_pci.c
Simple merge