net: Make dn_ptr depend on CONFIG_DECNET

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -1800,7 +1800,9 @@ struct net_device {
 #endif
 	void 			*atalk_ptr;
 	struct in_device __rcu	*ip_ptr;
+#if IS_ENABLED(CONFIG_DECNET)
 	struct dn_dev __rcu     *dn_ptr;
+#endif
 	struct inet6_dev __rcu	*ip6_ptr;
 	void			*ax25_ptr;
 	struct wireless_dev	*ieee80211_ptr;

net/core/dev.c

@@ -8134,8 +8134,9 @@ void netdev_run_todo(void)
 		BUG_ON(!list_empty(&dev->ptype_specific));
 		WARN_ON(rcu_access_pointer(dev->ip_ptr));
 		WARN_ON(rcu_access_pointer(dev->ip6_ptr));
+#if IS_ENABLED(CONFIG_DECNET)
 		WARN_ON(dev->dn_ptr);
-
+#endif
 		if (dev->priv_destructor)
 			dev->priv_destructor(dev);
 		if (dev->needs_free_netdev)