ipv4/route: arg delay is useless in rt_cache_flush()

Since route cache deletion (89aef8921bfbac22f), delay is no
more used. Remove it.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/route.h b/include/net/route.h
index 776a27f..da22243 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -108,7 +108,7 @@
 
 struct in_device;
 extern int		ip_rt_init(void);
-extern void		rt_cache_flush(struct net *net, int how);
+extern void		rt_cache_flush(struct net *net);
 extern void		rt_flush_dev(struct net_device *dev);
 extern struct rtable *__ip_route_output_key(struct net *, struct flowi4 *flp);
 extern struct rtable *ip_route_output_flow(struct net *, struct flowi4 *flp,