ath9k: dynack: make ewma estimation faster

In order to make propagation time estimation faster,
use current sample as ewma output value during 'late ack'
tracking

Tested-by: Koen Vandeputte <koen.vandeputte@ncentric.com>
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

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>