fix multi-axes set, reset, compare

Author: thinkyhead

Marlin/src/module/ft_motion.h

@@ -287,7 +287,7 @@ class FTMotion {
           #undef _HANDLE_DIR_CHANGES
         }
 
-        if (stepper_plan.advance_dividend_q0_32 == 0) {
+        if ((bool)stepper_plan.advance_dividend_q0_32) {
           // don't waste time in zero motion traj points
           bresenham_iterations_pending = 0;
           step_bits = 0;

Marlin/src/module/ft_types.h

@@ -47,7 +47,7 @@ enum dynFreqMode_t : uint8_t {
 typedef struct stepper_plan {
   AxisBits dir_bits;
   xyze_ulong_t advance_dividend_q0_32{0};
-  void reset() { advance_dividend_q0_32 = 0; }
+  void reset() { advance_dividend_q0_32.reset(); }
 } stepper_plan_t;
 
 // Emitters for code that only cares about shaped XYZE