wifi: mac80211: mlme: Fix missing unlock on beacon RX

Commit 98b0b46746 ("wifi: mac80211: mlme: use correct link_sta")
switched to link station instead of deflink and added some checks to do
that, which are done with the 'sta_mtx' mutex held. However, the error
path of these checks does not unlock 'sta_mtx' before returning.

Fixes: 98b0b46746 ("wifi: mac80211: mlme: use correct link_sta")
Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com>
Link: https://lore.kernel.org/r/20220924184042.778676-1-rafaelmendsr@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/mlme.c

@@ -5589,12 +5589,16 @@ static void ieee80211_rx_mgmt_beacon(struct ieee80211_link_data *link,
 
 	mutex_lock(&local->sta_mtx);
 	sta = sta_info_get(sdata, sdata->vif.cfg.ap_addr);
-	if (WARN_ON(!sta))
+	if (WARN_ON(!sta)) {
+		mutex_unlock(&local->sta_mtx);
 		goto free;
+	}
 	link_sta = rcu_dereference_protected(sta->link[link->link_id],
 					     lockdep_is_held(&local->sta_mtx));
-	if (WARN_ON(!link_sta))
+	if (WARN_ON(!link_sta)) {
+		mutex_unlock(&local->sta_mtx);
 		goto free;
+	}
 
 	changed |= ieee80211_recalc_twt_req(link, link_sta, elems);