fix(_serial): change _serial to _software_serial and add #ifdef block

Author: asas1asas200

src/rdm6300.cpp

@@ -118,12 +118,14 @@ uint32_t Rdm6300::get_tag_id(void)
 	return tag_id;
 }
 
+#ifdef RDM6300_SOFTWARE_SERIAL
 void Rdm6300::listen(void)
 {
-	_serial->listen();
+	_software_serial->listen();
 }
 
 bool Rdm6300::is_listening(void)
 {
-	return _serial->isListening();
+	return _software_serial->isListening();
 }
+#endif

src/rdm6300.h

@@ -40,8 +40,10 @@ class Rdm6300
 		bool update(void);
 		uint32_t get_tag_id(void);
 		bool is_tag_near(void);
+#ifdef RDM6300_SOFTWARE_SERIAL
 		void listen(void);
 		bool is_listening(void);
+#endif
 	private:
 #ifdef RDM6300_HARDWARE_SERIAL
 		HardwareSerial *_hardware_serial = NULL;