Make AX.25, DMR, P25, NXDN and FM selectable at compile time.

AX25Frame.cpp

@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_AX25)
+
 #include "Globals.h"
 #include "AX25Frame.h"
 
@@ -120,3 +123,5 @@ void CAX25Frame::addCRC()
   m_data[m_length++] = crc8[1U];
 }
 
+#endif
+