rt2x00: fix rmmod crash

Avoid queue and run autowakeup_work when device is not present anymore.
That prevent rmmod and device remove crash introduced by:

commit 1c0bcf89d85cc97a0d9ce4cd909351a81fa4fdde
Author: Ivo van Doorn <ivdoorn@gmail.com>
Date:   Sat Apr 30 17:18:18 2011 +0200

    rt2x00: Add autowake support for USB hardware

Signed-off-by: Stanislaw Gruszka <stf_xl@wp.pl>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2x00config.c

@@ -250,7 +250,8 @@ void rt2x00lib_config(struct rt2x00_dev *rt2x00dev,
 	if (ieee80211_flags & IEEE80211_CONF_CHANGE_CHANNEL)
 		rt2x00link_reset_tuner(rt2x00dev, false);
 
-	if (test_bit(REQUIRE_PS_AUTOWAKE, &rt2x00dev->cap_flags) &&
+	if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags) &&
+	    test_bit(REQUIRE_PS_AUTOWAKE, &rt2x00dev->cap_flags) &&
 	    (ieee80211_flags & IEEE80211_CONF_CHANGE_PS) &&
 	    (conf->flags & IEEE80211_CONF_PS)) {
 		beacon_diff = (long)jiffies - (long)rt2x00dev->last_beacon;

drivers/net/wireless/rt2x00/rt2x00dev.c

@@ -146,6 +146,9 @@ static void rt2x00lib_autowakeup(struct work_struct *work)
 	struct rt2x00_dev *rt2x00dev =
 	    container_of(work, struct rt2x00_dev, autowakeup_work.work);
 
+	if (!test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
+		return;
+
 	if (rt2x00dev->ops->lib->set_device_state(rt2x00dev, STATE_AWAKE))
 		ERROR(rt2x00dev, "Device failed to wakeup.\n");
 	clear_bit(CONFIG_POWERSAVING, &rt2x00dev->flags);
@@ -1160,6 +1163,7 @@ void rt2x00lib_remove_dev(struct rt2x00_dev *rt2x00dev)
 	 * Stop all work.
 	 */
 	cancel_work_sync(&rt2x00dev->intf_work);
+	cancel_delayed_work_sync(&rt2x00dev->autowakeup_work);
 	if (rt2x00_is_usb(rt2x00dev)) {
 		del_timer_sync(&rt2x00dev->txstatus_timer);
 		cancel_work_sync(&rt2x00dev->rxdone_work);