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/pulses/multi.cpp

@@ -116,12 +116,9 @@ static void sendFailsafeChannels(uint8_t*& p_buf, uint8_t module)
 static void setupPulsesMulti(uint8_t*& p_buf, uint8_t module)
 {
   static int counter[2] = {0,0}; //TODO
-  static uint8_t invert[2] = {0x00,        //internal
-#if defined(PCBTARANIS) || defined(PCBHORUS) || defined(PCBNV14)
+  static uint8_t invert[2] = {
+    0x00,       //internal
     0x08        //external
-#else
-    0x00	//external
-#endif
   };
   uint8_t type=MULTI_NORMAL;