mac80211: notify driver for change in multicast rates

With drivers implementing rate control in driver or firmware
rate_control_send_low() may not get called, and thus the
driver needs to know about changes in the multicast rate.

Add and use a new BSS change flag for this.

Signed-off-by: Pradeep Kumar Chitrapu <pradeepc@codeaurora.org>
[rewrite commit message]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
index 6a381cb..d51da26 100644
--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -880,7 +880,8 @@ int ieee80211_start_mesh(struct ieee80211_sub_if_data *sdata)
 		      BSS_CHANGED_BEACON_ENABLED |
 		      BSS_CHANGED_HT |
 		      BSS_CHANGED_BASIC_RATES |
-		      BSS_CHANGED_BEACON_INT;
+		      BSS_CHANGED_BEACON_INT |
+		      BSS_CHANGED_MCAST_RATE;
 
 	local->fif_other_bss++;
 	/* mesh ifaces must set allmulti to forward mcast traffic */