[NET] NETNS: Omit net_device->nd_net without CONFIG_NET_NS.

Introduce per-net_device inlines: dev_net(), dev_net_set().
Without CONFIG_NET_NS, no namespace other than &init_net exists.
Let's explicitly define them to help compiler optimizations.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 36b9f22..2759b76 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -599,7 +599,7 @@
 	struct dev_rcv_lists *d;
 	int matches;
 
-	if (dev->type != ARPHRD_CAN || dev->nd_net != &init_net) {
+	if (dev->type != ARPHRD_CAN || dev_net(dev) != &init_net) {
 		kfree_skb(skb);
 		return 0;
 	}
@@ -710,7 +710,7 @@
 	struct net_device *dev = (struct net_device *)data;
 	struct dev_rcv_lists *d;
 
-	if (dev->nd_net != &init_net)
+	if (dev_net(dev) != &init_net)
 		return NOTIFY_DONE;
 
 	if (dev->type != ARPHRD_CAN)