fix #346 limit tx power in japan

src/mesh/RadioInterface.h

@@ -119,6 +119,12 @@ class RadioInterface : protected concurrency::NotifiedWorkerThread
 
     virtual void loop() {} // Idle processing
 
+    /**
+     * Some regulatory regions limit xmit power.
+     * This function should be called by subclasses after setting their desired power.  It might lower it
+     */
+    void limitPower();
+
     /**
      * Convert our modemConfig enum into wf, sf, etc...
      *