Tweak babystep add_steps

Marlin/src/feature/babystep.cpp

   add_steps(axis, mm * planner.settings.axis_steps_per_mm[axis]);
 }
 
-void Babystep::add_steps(const AxisEnum axis, const int32_t distance) {
+void Babystep::add_steps(const AxisEnum axis, const int16_t distance) {
 
   #if ENABLED(BABYSTEP_WITHOUT_HOMING)
     #define CAN_BABYSTEP(AXIS) true

Marlin/src/feature/babystep.h

       }
     #endif
   #endif
-  static void add_steps(const AxisEnum axis, const int32_t distance);
+  static void add_steps(const AxisEnum axis, const int16_t distance);
   static void add_mm(const AxisEnum axis, const float &mm);
   static void task();
 private: