rtl818x: Remove SKB list assumptions.

Eliminate the assumption that SKBs and SKB list heads can
be cast to eachother in SKB list handling code.
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wireless/realtek/rtl818x/rtl8187/dev.c

@@ -499,7 +499,7 @@ static void rtl8187b_status_cb(struct urb *urb)
 	if (cmd_type == 1) {
 		unsigned int pkt_rc, seq_no;
 		bool tok;
-		struct sk_buff *skb;
+		struct sk_buff *skb, *iter;
 		struct ieee80211_hdr *ieee80211hdr;
 		unsigned long flags;
 
@@ -508,8 +508,9 @@ static void rtl8187b_status_cb(struct urb *urb)
 		seq_no = (val >> 16) & 0xFFF;
 
 		spin_lock_irqsave(&priv->b_tx_status.queue.lock, flags);
-		skb_queue_reverse_walk(&priv->b_tx_status.queue, skb) {
-			ieee80211hdr = (struct ieee80211_hdr *)skb->data;
+		skb = NULL;
+		skb_queue_reverse_walk(&priv->b_tx_status.queue, iter) {
+			ieee80211hdr = (struct ieee80211_hdr *)iter->data;
 
 			/*
 			 * While testing, it was discovered that the seq_no
@@ -522,10 +523,12 @@ static void rtl8187b_status_cb(struct urb *urb)
 			 * it's unlikely we wrongly ack some sent data
 			 */
 			if ((le16_to_cpu(ieee80211hdr->seq_ctrl)
-			    & 0xFFF) == seq_no)
+			     & 0xFFF) == seq_no) {
+				skb = iter;
 				break;
 			}
-		if (skb != (struct sk_buff *) &priv->b_tx_status.queue) {
+		}
+		if (skb) {
 			struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 
 			__skb_unlink(skb, &priv->b_tx_status.queue);