mac80211: sync dtim_count to TSF

On starting a mesh or AP BSS, the interface dtim_count
countdown should match that of the driver TSF.

Signed-off-by: Thomas Pedersen <twpedersen@gmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
index 5a74b24..5b919ca 100644
--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -807,6 +807,7 @@
 		return -ENOMEM;
 	}
 
+	ieee80211_recalc_dtim(local, sdata);
 	ieee80211_bss_info_change_notify(sdata, changed);
 
 	netif_carrier_on(sdata->dev);