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/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index fa6c905..6beaff5 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -159,6 +159,9 @@
 /* return block-ack bitmap index given sequence and starting sequence */
 #define ATH_BA_INDEX(_st, _seq) (((_seq) - (_st)) & (IEEE80211_SEQ_MAX - 1))
 
+/* return the seqno for _start + _offset */
+#define ATH_BA_INDEX2SEQ(_seq, _offset) (((_seq) + (_offset)) & (IEEE80211_SEQ_MAX - 1))
+
 /* returns delimiter padding required given the packet length */
 #define ATH_AGGR_GET_NDELIM(_len)					\
        (((_len) >= ATH_AGGR_MINPLEN) ? 0 :                             \
@@ -252,9 +255,9 @@
 struct ath_node {
 #ifdef CONFIG_ATH9K_DEBUGFS
 	struct list_head list; /* for sc->nodes */
+#endif
 	struct ieee80211_sta *sta; /* station struct we're part of */
 	struct ieee80211_vif *vif; /* interface with which we're associated */
-#endif
 	struct ath_atx_tid tid[WME_NUM_TID];
 	struct ath_atx_ac ac[WME_NUM_AC];
 	int ps_key;
@@ -276,7 +279,6 @@
 };
 
 #define ATH_TX_ERROR        0x01
-#define ATH_TX_BAR          0x02
 
 /**
  * @txq_map:  Index is mac80211 queue number.  This is