net: Print num_rx_queues imbalance warning only when there are allocated queues

BugLink: http://bugs.launchpad.net/bugs/591416

There are a number of network drivers (bridge, bonding, etc) that are not yet
receive multi-queue enabled and use alloc_netdev(), so don't print a
num_rx_queues imbalance warning in that case.

Also, only print the warning once for those drivers that _are_ multi-queue
enabled.
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

net/core/dev.c

@@ -2253,11 +2253,9 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 	if (skb_rx_queue_recorded(skb)) {
 		u16 index = skb_get_rx_queue(skb);
 		if (unlikely(index >= dev->num_rx_queues)) {
-			if (net_ratelimit()) {
-				pr_warning("%s received packet on queue "
-					"%u, but number of RX queues is %u\n",
-					dev->name, index, dev->num_rx_queues);
-			}
+			WARN_ONCE(dev->num_rx_queues > 1, "%s received packet "
+				"on queue %u, but number of RX queues is %u\n",
+				dev->name, index, dev->num_rx_queues);
 			goto done;
 		}
 		rxqueue = dev->_rx + index;