tweak HAL_timer_start

Author: thinkyhead

Marlin/src/HAL/AVR/timers.h

@@ -66,17 +66,17 @@ FORCE_INLINE void HAL_timer_start(const uint8_t timer_num, const uint32_t) {
   switch (timer_num) {
     case MF_TIMER_STEP:
       // waveform generation = 0100 = CTC
-      SET_WGM(1, CTC_OCRnA);
+      SET_WGM(MF_TIMER_STEP, CTC_OCRnA);
 
       // output mode = 00 (disconnected)
-      SET_COMA(1, NORMAL);
+      SET_COMA(MF_TIMER_STEP, NORMAL);
 
       // Set the timer pre-scaler
       // Generally we use a divider of 8, resulting in a 2MHz timer
       // frequency on a 16MHz MCU. If you are going to change this, be
       // sure to regenerate speed_lookuptable.h with
       // create_speed_lookuptable.py
-      SET_CS(1, PRESCALER_8);  //  CS 2 = 1/8 prescaler
+      SET_CS(MF_TIMER_STEP, PRESCALER_8);  //  CS 2 = 1/8 prescaler
 
       // Init Stepper ISR to 122 Hz for quick starting
       // (F_CPU) / (STEPPER_TIMER_PRESCALE) / frequency