ath9k: fix false positives in the baseband hang check

ath9k_hw_check_alive() occasionally returns false, as the hardware
is still processing data in a specific state. Fix this issue by
repeating the test a few times with longer delay inbetween attempts.
This gets rid of excessive hardware resets that appear frequently on
some AR9132 based devices, but could also happen on AR9280.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Reported-by: Björn Smedman <bjorn.smedman@venatech.se>
Cc: stable@kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/init.c b/drivers/net/wireless/ath/ath9k/init.c
index 8700e3d..fe730cb 100644
--- a/drivers/net/wireless/ath/ath9k/init.c
+++ b/drivers/net/wireless/ath/ath9k/init.c
@@ -718,6 +718,7 @@
 			goto error_world;
 	}
 
+	INIT_WORK(&sc->hw_check_work, ath_hw_check);
 	INIT_WORK(&sc->paprd_work, ath_paprd_calibrate);
 	INIT_WORK(&sc->chan_work, ath9k_wiphy_chan_work);
 	INIT_DELAYED_WORK(&sc->wiphy_work, ath9k_wiphy_work);