fib: Use const struct nl_info * in rtmsg_fib

The rtmsg_fib function doesn't modify this argument so mark
it const.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index d5dbca5..e63f47a 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -380,7 +380,7 @@
 }
 
 void rtmsg_fib(int event, __be32 key, struct fib_alias *fa,
-	       int dst_len, u32 tb_id, struct nl_info *info,
+	       int dst_len, u32 tb_id, const struct nl_info *info,
 	       unsigned int nlm_flags)
 {
 	struct sk_buff *skb;