mac80211_hwsim: fix unregistration

If you rmmod the module while associated, frames might
be transmitted during unregistration -- which will crash
if the hwsim%d interface is unregistered first, so only
do that after all the virtual wiphys are gone.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/mac80211_hwsim.c

@@ -1167,8 +1167,8 @@ static void __exit exit_mac80211_hwsim(void)
 {
 	printk(KERN_DEBUG "mac80211_hwsim: unregister radios\n");
 
-	unregister_netdev(hwsim_mon);
 	mac80211_hwsim_free();
+	unregister_netdev(hwsim_mon);
 }