virtio-net: fix total qstat values

NIPA tests report that the interface statistics reported
via qstat are lower than those reported via ip link.
Looks like this is because some tests flip the queue
count up and down, and we end up with some of the traffic
accounted on disabled queues.

Add up counters from disabled queues.

Fixes: d888f04 ("virtio-net: support queue stat")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Link: https://patch.msgid.link/20250507003221.823267-3-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/virtio_net.c

@@ -5678,6 +5678,10 @@ static void virtnet_get_base_stats(struct net_device *dev,
 
 	if (vi->device_stats_cap & VIRTIO_NET_STATS_TYPE_TX_SPEED)
 		tx->hw_drop_ratelimits = 0;
+
+	netdev_stat_queue_sum(dev,
+			      dev->real_num_rx_queues, vi->max_queue_pairs, rx,
+			      dev->real_num_tx_queues, vi->max_queue_pairs, tx);
 }
 
 static const struct netdev_stat_ops virtnet_stat_ops = {