fix(ui): Auto adjust PPM frame length if greater than 8 ch (#3622)

* Auto-adjusts PPM frame length if channel count is greater than 8 channels

* added auto adjust for PPM trainer mode on b&w targets

* code cleanup

radio/src/gui/128x64/model_setup.cpp

@@ -1489,6 +1489,8 @@ void menuModelSetup(event_t event)
               break;
             case 1:
               CHECK_INCDEC_MODELVAR(event, g_model.trainerData.channelsCount, -4, min<int8_t>(MAX_TRAINER_CHANNELS_M8, 32-8-g_model.trainerData.channelsStart));
+              if (checkIncDec_Ret)
+                setDefaultPpmFrameLengthTrainer();
               break;
           }
         }