mac80211: simplify ieee80211_add_station()

There's no need to do some kind of weird err and RCU dance
just use sta_info_insert() directly.

Link: https://lore.kernel.org/r/20210517230754.55abd10056c0.I6f5a3b7b23347b2cdaf64e6d5ce1d9e904059654@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/cfg.c

@@ -1693,15 +1693,7 @@ static int ieee80211_add_station(struct wiphy *wiphy, struct net_device *dev,
 	    test_sta_flag(sta, WLAN_STA_ASSOC))
 		rate_control_rate_init(sta);
 
-	err = sta_info_insert_rcu(sta);
-	if (err) {
-		rcu_read_unlock();
-		return err;
-	}
-
-	rcu_read_unlock();
-
-	return 0;
+	return sta_info_insert(sta);
 }
 
 static int ieee80211_del_station(struct wiphy *wiphy, struct net_device *dev,