mac80211: cancel the connection monitor timers/work

In "mac80211: monitor the connection" I forgot to
add code to cancel the new timers & work when the
interface is brought down, which isn't a problem
if you just bring it down, but _is_ a problem when
you destroy the interface. Correct this lapse.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 18dad22..e3b3156 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -1163,6 +1163,9 @@
 	const u8 *ssid;
 	bool already = false;
 
+	if (!netif_running(sdata->dev))
+		return;
+
 	mutex_lock(&ifmgd->mtx);
 
 	if (!ifmgd->associated)