rt2x00: Don't queue ieee80211 work after USB removal

This prevents the rt2x00 driver from queueing ieee80211 work after the  
USB card has been removed, preventing a kernel panic.

Signed-off-by: Sean Cross <sean@chumby.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rt2x00/rt2x00link.c b/drivers/net/wireless/rt2x00/rt2x00link.c
index c64db0b..c708d0b 100644
--- a/drivers/net/wireless/rt2x00/rt2x00link.c
+++ b/drivers/net/wireless/rt2x00/rt2x00link.c
@@ -362,8 +362,9 @@
 
 	rt2x00link_reset_tuner(rt2x00dev, false);
 
-	ieee80211_queue_delayed_work(rt2x00dev->hw,
-				     &link->work, LINK_TUNE_INTERVAL);
+	if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
+		ieee80211_queue_delayed_work(rt2x00dev->hw,
+					     &link->work, LINK_TUNE_INTERVAL);
 }
 
 void rt2x00link_stop_tuner(struct rt2x00_dev *rt2x00dev)
@@ -469,8 +470,10 @@
 	 * Increase tuner counter, and reschedule the next link tuner run.
 	 */
 	link->count++;
-	ieee80211_queue_delayed_work(rt2x00dev->hw,
-				     &link->work, LINK_TUNE_INTERVAL);
+
+	if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
+		ieee80211_queue_delayed_work(rt2x00dev->hw,
+					     &link->work, LINK_TUNE_INTERVAL);
 }
 
 void rt2x00link_register(struct rt2x00_dev *rt2x00dev)