ath9k: Fix kernel panic on module unload

The commit "ath9k: configure beacons based on hw opmode" introduced
a regression which leads to kernel panic. Failed to stop ani timer
during the driver unload while any of the beaconing vif is running.

Signed-off-by: Rajkumar Manoharan <rmanoharan@atheros.com>
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 93b9fa2..a55a892 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -1375,6 +1375,9 @@
 	if ((iter_data.naps + iter_data.nadhocs) > 0) {
 		sc->sc_flags |= SC_OP_ANI_RUN;
 		ath_start_ani(common);
+	} else {
+		sc->sc_flags &= ~SC_OP_ANI_RUN;
+		del_timer_sync(&common->ani.timer);
 	}
 }