[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/ip_fib.h b/include/net/ip_fib.h
index 5a4a0366..69252cb 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -213,7 +213,7 @@
 #endif /* CONFIG_IP_MULTIPLE_TABLES */
 
 /* Exported by fib_frontend.c */
-extern struct nla_policy rtm_ipv4_policy[];
+extern const struct nla_policy rtm_ipv4_policy[];
 extern void		ip_fib_init(void);
 extern int fib_validate_source(__be32 src, __be32 dst, u8 tos, int oif,
 			       struct net_device *dev, __be32 *spec_dst, u32 *itag);