feat(radio): Discover SBUS trainer availability (#4266)

Co-authored-by: raphaelcoeffic <1050031+raphaelcoeffic@users.noreply.github.com>
Co-authored-by: Peter Feerick <peter.feerick@gmail.com>

radio/src/tasks/mixer_task.cpp

@@ -122,10 +122,8 @@ constexpr uint8_t MIXER_MAX_PERIOD = MAX_REFRESH_RATE / 1000 /*ms*/;
 
 void execMixerFrequentActions()
 {
-#if defined(SBUS_TRAINER)
   // SBUS trainer
   processSbusInput();
-#endif
 
 #if defined(IMU)
   gyro.wakeup();