[NETLINK]: Mark netlink policies const

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/fib_rules.h b/include/net/fib_rules.h
index ed3a887..83e41dd 100644
--- a/include/net/fib_rules.h
+++ b/include/net/fib_rules.h
@@ -64,7 +64,7 @@
 	void			(*flush_cache)(void);
 
 	int			nlgroup;
-	struct nla_policy	*policy;
+	const struct nla_policy	*policy;
 	struct list_head	*rules_list;
 	struct module		*owner;
 };