ath9k: reduce the number of unnecessary BAR tx packets

When processing A-MPDU tx status, only send a BAR for the failed packet
with the highest sequence number.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index 7d92004..4475b0d 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -644,9 +644,9 @@
 	spin_lock(&sc->nodes_lock);
 	list_add(&an->list, &sc->nodes);
 	spin_unlock(&sc->nodes_lock);
+#endif
 	an->sta = sta;
 	an->vif = vif;
-#endif
 	if (sc->sc_flags & SC_OP_TXAGGR) {
 		ath_tx_node_init(sc, an);
 		an->maxampdu = 1 << (IEEE80211_HT_MAX_AMPDU_FACTOR +