Correct type of _frequency from int to long

Author: torntrousers

src/LoRa.h

@@ -85,7 +85,7 @@ class LoRaClass : public Stream {
   int _ss;
   int _reset;
   int _dio0;
-  int _frequency;
+  long _frequency;
   int _packetIndex;
   int _implicitHeaderMode;
   void (*_onReceive)(int);