b43: Don't abuse wl->current_dev in the led work

Don't abuse wl->current_dev in the LED work for checking whether we're
going down. Add an explicit variable.
This fixes a crash on rmmod dereferencing the wl->current_dev NULL pointer
in various other places of the driver.
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/b43/leds.c

@@ -112,10 +112,7 @@ static void b43_led_brightness_set(struct led_classdev *led_dev,
 	struct b43_led *led = container_of(led_dev, struct b43_led, led_dev);
 	struct b43_wl *wl = led->wl;
 
-	/* The check for current_dev is only needed while unregistering,
-	 * so it is sequencial and does not race. But we must not dereference
-	 * current_dev here. */
-	if (likely(wl->current_dev)) {
+	if (likely(!wl->leds.stop)) {
 		atomic_set(&led->state, brightness);
 		ieee80211_queue_work(wl->hw, &wl->leds.work);
 	}
@@ -314,6 +311,8 @@ void b43_leds_init(struct b43_wldev *dev)
 			break;
 		}
 	}
+
+	dev->wl->leds.stop = 0;
 }
 
 void b43_leds_exit(struct b43_wldev *dev)

drivers/net/wireless/b43/leds.h

@@ -35,6 +35,7 @@ struct b43_leds {
 	struct b43_led led_radio;
 	struct b43_led led_assoc;
 
+	bool stop;
 	struct work_struct work;
 };
 

drivers/net/wireless/b43/main.c

@@ -4987,7 +4987,7 @@ static void b43_remove(struct ssb_device *dev)
 		 * might have modified it. Restoring is important, so the networking
 		 * stack can properly free resources. */
 		wl->hw->queues = wl->mac80211_initially_registered_queues;
-		wl->current_dev = NULL;
+		wl->leds.stop = 1;
 		cancel_work_sync(&wl->leds.work);
 		ieee80211_unregister_hw(wl->hw);
 	}