net: sched: mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_prio.c b/net/sched/sch_prio.c
index 95fad34..2c79559 100644
--- a/net/sched/sch_prio.c
+++ b/net/sched/sch_prio.c
@@ -50,6 +50,7 @@ prio_classify(struct sk_buff *skb, struct Qdisc *sch, int *qerr)
 		case TC_ACT_QUEUED:
 		case TC_ACT_TRAP:
 			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
+			/* fall through */
 		case TC_ACT_SHOT:
 			return NULL;
 		}