net: CONFIG_NET_NS reduction

Use read_pnet() and write_pnet() to reduce number of ifdef CONFIG_NET_NS

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index a249161..bd6b753 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1087,11 +1087,7 @@
 static inline
 struct net *dev_net(const struct net_device *dev)
 {
-#ifdef CONFIG_NET_NS
-	return dev->nd_net;
-#else
-	return &init_net;
-#endif
+	return read_pnet(&dev->nd_net);
 }
 
 static inline