mac80211: assign bss_conf.bssid only once

Instead of checking every time bss_info_changed is called,
assign the pointer once depending on the interface type
and then leave it untouched until the interface type is
changed. This makes the ieee80211_bss_info_change_notify()
now a simple wrapper to call the driver only.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
index fcfa7ef9..2458858 100644
--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -810,6 +810,7 @@
 void ieee80211_mesh_init_sdata(struct ieee80211_sub_if_data *sdata)
 {
 	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
+	static u8 zero_addr[ETH_ALEN] = {};
 
 	setup_timer(&ifmsh->housekeeping_timer,
 		    ieee80211_mesh_housekeeping_timer,
@@ -835,4 +836,6 @@
 	INIT_LIST_HEAD(&ifmsh->preq_queue.list);
 	spin_lock_init(&ifmsh->mesh_preq_queue_lock);
 	spin_lock_init(&ifmsh->sync_offset_lock);
+
+	sdata->vif.bss_conf.bssid = zero_addr;
 }