b43: Fix possible MMIO access while device is down

This fixes a possible MMIO access while the device is still down
from a suspend cycle. MMIO accesses with the device powered down
may cause crashes on certain devices.
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/b43/leds.c

@@ -72,6 +72,9 @@ static void b43_led_brightness_set(struct led_classdev *led_dev,
 	struct b43_wldev *dev = led->dev;
 	bool radio_enabled;
 
+	if (unlikely(b43_status(dev) < B43_STAT_INITIALIZED))
+		return;
+
 	/* Checking the radio-enabled status here is slightly racy,
 	 * but we want to avoid the locking overhead and we don't care
 	 * whether the LED has the wrong state for a second. */