mac80211: fix offchannel TX cookie matching

When I introduced in-kernel off-channel TX I
introduced a bug -- the work can't be canceled
again because the code clear the skb pointer.
Fix this by keeping track separately of whether
TX status has already been reported.

Cc: stable@kernel.org [2.6.38+]
Reported-by: Jouni Malinen <j@w1.fi>
Tested-by: Jouni Malinen <j@w1.fi>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 1309bb9..d0705f2 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1886,7 +1886,7 @@
 	 * so in that case userspace will have to deal with it.
 	 */
 
-	if (wk->offchan_tx.wait && wk->offchan_tx.frame)
+	if (wk->offchan_tx.wait && !wk->offchan_tx.status)
 		cfg80211_mgmt_tx_status(wk->sdata->dev,
 					(unsigned long) wk->offchan_tx.frame,
 					wk->ie, wk->ie_len, false, GFP_KERNEL);