net-sched: change tcf_destroy_chain() to clear start of filter list

Pass double tcf_proto pointers to tcf_destroy_chain() to make it
clear the start of the filter list for more consistency.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index c40773c..10f01ad 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1252,12 +1252,12 @@
 	kfree(tp);
 }
 
-void tcf_destroy_chain(struct tcf_proto *fl)
+void tcf_destroy_chain(struct tcf_proto **fl)
 {
 	struct tcf_proto *tp;
 
-	while ((tp = fl) != NULL) {
-		fl = tp->next;
+	while ((tp = *fl) != NULL) {
+		*fl = tp->next;
 		tcf_destroy(tp);
 	}
 }