mac80211: disable IBSS beacon before join

Before we have a probe response frame (which is used as the
beacon too) there's no need to ask drivers to beacon, they
will not get a beacon anyway.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/main.c

@@ -210,6 +210,8 @@ int ieee80211_if_config(struct ieee80211_sub_if_data *sdata, u32 changed)
 					!!rcu_dereference(sdata->u.ap.beacon);
 				break;
 			case NL80211_IFTYPE_ADHOC:
+				conf.enable_beacon = !!sdata->u.sta.probe_resp;
+				break;
 			case NL80211_IFTYPE_MESH_POINT:
 				conf.enable_beacon = true;
 				break;