mac80211: don't reinit rate control when mesh sta exists

This fixes some unintended resets of the rate control statistics
when minstrel_ht is used resulting in non-optimal throughput on mesh
links.
Tested-by: Emanuel Taube <emanuel.taube@gmail.com>
Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/mesh_plink.c

@@ -391,6 +391,7 @@ static struct sta_info *mesh_peer_init(struct ieee80211_sub_if_data *sdata,
 		sta->ch_width = chandef.width;
 	}
 
+	if (insert)
 		rate_control_rate_init(sta);
 	spin_unlock_bh(&sta->lock);