net: push loops and nb calls into helper functions

Push iterations over net namespaces and netdevices from
register_netdevice_notifier() and unregister_netdevice_notifier()
into helper functions. Along with that introduce continue_reverse macros
to make the code a bit nicer allowing to get rid of "last" marks.

Signed-off-by: Jiri Pirko <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index f8712bb..c5a98e0 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -317,7 +317,8 @@ static inline struct net *read_pnet(const possible_net_t *pnet)
 /* Protected by net_rwsem */
 #define for_each_net(VAR)				\
 	list_for_each_entry(VAR, &net_namespace_list, list)
-
+#define for_each_net_continue_reverse(VAR)		\
+	list_for_each_entry_continue_reverse(VAR, &net_namespace_list, list)
 #define for_each_net_rcu(VAR)				\
 	list_for_each_entry_rcu(VAR, &net_namespace_list, list)