Ath5k: kill tasklets on shutdown

Don't forget to kill tasklets on stop to not panic if they
fire after freeing some structures.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Acked-by: Nick Kossifidis <mickflemm@gmail.com>
Cc: Luis R. Rodriguez <mcgrof@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath5k/base.c

@@ -2342,6 +2342,9 @@ ath5k_stop_hw(struct ath5k_softc *sc)
 	mutex_unlock(&sc->lock);
 
 	del_timer_sync(&sc->calib_tim);
+	tasklet_kill(&sc->rxtq);
+	tasklet_kill(&sc->txtq);
+	tasklet_kill(&sc->restq);
 
 	return ret;
 }