Revert "Reset timer count before first block step"

This reverts commit 5cf6a062e3.

Marlin/src/module/stepper.h

@@ -362,6 +362,9 @@ class Stepper {
       OCR1A_nominal = calc_timer_interval(current_block->nominal_rate);
       // make a note of the number of step loops required at nominal speed
       step_loops_nominal = step_loops;
+      acc_step_rate = current_block->initial_rate;
+      acceleration_time = calc_timer_interval(acc_step_rate);
+      _NEXT_ISR(acceleration_time);
 
       #if ENABLED(LIN_ADVANCE)
         if (current_block->use_advance_lead) {