ath9k: Fix powersave locking

The 'ps_flags' is used/accessed in a variety of contexts
and requires proper locking. Use 'sc_pm_lock' appropriately.

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
index bb74780..f777ddc 100644
--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -1994,6 +1994,7 @@
 	struct ath_common *common = ath9k_hw_common(sc->sc_ah);
 	struct ieee80211_hdr * hdr = (struct ieee80211_hdr *)skb->data;
 	int q, padpos, padsize;
+	unsigned long flags;
 
 	ath_dbg(common, XMIT, "TX complete: skb: %p\n", skb);
 
@@ -2012,6 +2013,7 @@
 		skb_pull(skb, padsize);
 	}
 
+	spin_lock_irqsave(&sc->sc_pm_lock, flags);
 	if ((sc->ps_flags & PS_WAIT_FOR_TX_ACK) && !txq->axq_depth) {
 		sc->ps_flags &= ~PS_WAIT_FOR_TX_ACK;
 		ath_dbg(common, PS,
@@ -2021,6 +2023,7 @@
 					PS_WAIT_FOR_PSPOLL_DATA |
 					PS_WAIT_FOR_TX_ACK));
 	}
+	spin_unlock_irqrestore(&sc->sc_pm_lock, flags);
 
 	q = skb_get_queue_mapping(skb);
 	if (txq == sc->tx.txq_map[q]) {