feat: Flysky PL18 Support (#4105)

Co-authored-by: raphaelcoeffic <raphael.coeffic@frafos.com>
Co-authored-by: rotorman <risto.koiva@web.de>
Co-authored-by: Xy201207 <yaoxu@flysky.com>
Co-authored-by: Peter Feerick <peter.feerick@gmail.com>

radio/src/boards/generic_stm32/module_ports.cpp

@@ -28,6 +28,7 @@
 #include "board.h"
 #include "dataconstants.h"
 
+#if defined (HARDWARE_INTERNAL_MODULE)
 #if defined(INTMODULE_USART)
 
 #define INTMODULE_USART_IRQ_PRIORITY 5
@@ -110,7 +111,8 @@ extern "C" void INTMODULE_TIMER_IRQHandler()
 
 DEFINE_STM32_SOFTSERIAL_PORT(InternalModule, intmoduleTimer);
 
-#endif
+#endif // INTMODULE_USART
+#endif // HARDWARE_INTERNAL_MODULE
 
 #include "module_timer_driver.h"