station: fix NAI realms leak

After the known network refactor this string list was no longer set
into the network object. Now it should be freed in all cases after
the search.

src/station.c

@@ -478,6 +478,8 @@ static void station_anqp_response_cb(enum anqp_result result,
 
 	known_networks_foreach(match_nai_realms, &search);
 
+	l_strv_free(realms);
+
 request_done:
 	l_queue_remove(station->anqp_pending, entry);