Make compiling AX.25 conditional.

AX25Network.cpp

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2020 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2020,2023 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -18,10 +18,11 @@
 
 #include "AX25Network.h"
 #include "AX25Defines.h"
-#include "Defines.h"
 #include "Utils.h"
 #include "Log.h"
 
+#if defined(USE_AX25)
+
 #include <cstdio>
 #include <cassert>
 #include <cstring>
@@ -181,3 +182,6 @@ void CAX25Network::enable(bool enabled)
 		m_rxLength   = 0U;
 	}
 }
+
+#endif
+