wl12xx: don't indicate up PS-filtered dummy packets

Dummy packets are currently only sent on the system_hlid link. The
system_hlid link should never be filtered for PS (as it is not
a STA link). Even so, for correctness, don't indicate dummy packets up.
The skb does not belong to mac80211 and as such does not contain a
correct skb->cb.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>
diff --git a/drivers/net/wireless/wl12xx/ps.c b/drivers/net/wireless/wl12xx/ps.c
index 4b720b1..c15ebf2 100644
--- a/drivers/net/wireless/wl12xx/ps.c
+++ b/drivers/net/wireless/wl12xx/ps.c
@@ -199,15 +199,19 @@
 	unsigned long flags;
 	int filtered[NUM_TX_QUEUES];
 
-	/* filter all frames currently the low level queus for this hlid */
+	/* filter all frames currently in the low level queues for this hlid */
 	for (i = 0; i < NUM_TX_QUEUES; i++) {
 		filtered[i] = 0;
 		while ((skb = skb_dequeue(&wl->links[hlid].tx_queue[i]))) {
+			filtered[i]++;
+
+			if (WARN_ON(wl12xx_is_dummy_packet(wl, skb)))
+				continue;
+
 			info = IEEE80211_SKB_CB(skb);
 			info->flags |= IEEE80211_TX_STAT_TX_FILTERED;
 			info->status.rates[0].idx = -1;
 			ieee80211_tx_status_ni(wl->hw, skb);
-			filtered[i]++;
 		}
 	}