mac80211: fix configure_filter invocation after stop

Since configure_filter can sleep now, any multicast
configuration needed to be postponed to a work struct.
This, however, lead to a problem that we could queue
the work, stop the device and then afterwards invoke
configure_filter which may lead to driver hangs and is
a bug. To fix this, we can just cancel the filter work
since it's unnecessary to do after stopping the hw.

Since there are various places that call drv_stop, and
two of them do very similar things, the code for them
can be put into a shared function at the same time.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Reported-by: Lennert Buytenhek <buytenh@wantstofly.org>
Tested-by: Lennert Buytenhek <buytenh@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index b161301..5940e69 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -552,11 +552,7 @@
 	ieee80211_recalc_ps(local, -1);
 
 	if (local->open_count == 0) {
-		drv_stop(local);
-
-		ieee80211_led_radio(local, false);
-
-		flush_workqueue(local->workqueue);
+		ieee80211_stop_device(local);
 
 		tasklet_disable(&local->tx_pending_tasklet);
 		tasklet_disable(&local->tasklet);