net: sched: constify tcf_proto and tc_action

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/act_csum.c b/net/sched/act_csum.c
index 6cdf9ab..453a734 100644
--- a/net/sched/act_csum.c
+++ b/net/sched/act_csum.c
@@ -500,7 +500,7 @@
 }
 
 static int tcf_csum(struct sk_buff *skb,
-		    struct tc_action *a, struct tcf_result *res)
+		    const struct tc_action *a, struct tcf_result *res)
 {
 	struct tcf_csum *p = a->priv;
 	int action;