mac80211: use skb list for fragments

We are currently linking the skbs by using skb->next
directly. This works, but the preferred way is to use
a struct sk_buff_head instead. That also prepares for
passing that to drivers directly.

While at it I noticed we calculate the duration for
fragments twice -- remove one of them.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 4cf25b0..939bf24 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -95,13 +95,13 @@
 
 void ieee80211_tx_set_protected(struct ieee80211_tx_data *tx)
 {
-	struct sk_buff *skb = tx->skb;
+	struct sk_buff *skb;
 	struct ieee80211_hdr *hdr;
 
-	do {
+	skb_queue_walk(&tx->skbs, skb) {
 		hdr = (struct ieee80211_hdr *) skb->data;
 		hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
-	} while ((skb = skb->next));
+	}
 }
 
 int ieee80211_frame_duration(struct ieee80211_local *local, size_t len,