net_sched: nla_memdup_cookie() can be static

Fixes the following sparse warning:

net/sched/act_api.c:532:5: warning:
 symbol 'nla_memdup_cookie' was not declared. Should it be static?

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/act_api.c

@@ -529,7 +529,7 @@ errout:
 	return err;
 }
 
-int nla_memdup_cookie(struct tc_action *a, struct nlattr **tb)
+static int nla_memdup_cookie(struct tc_action *a, struct nlattr **tb)
 {
 	a->act_cookie = kzalloc(sizeof(*a->act_cookie), GFP_KERNEL);
 	if (!a->act_cookie)