ath9k: add dynamic ACK timeout estimation

Add dynamic ACK timeout estimation algorithm based on ACK frame RX timestamp,
TX frame timestamp and frame duration.

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
Tested-by: Philippe Duchein <wireless-dev@duchein.net>
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 dd0f97f..8cd116e 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -274,6 +274,9 @@
 	struct ath_rx_rate_stats rx_rate_stats;
 #endif
 	u8 key_idx[4];
+
+	u32 ackto;
+	struct list_head list;
 };
 
 struct ath_tx_control {