stepper_enable: Move motor_off() logic to stepper_enable.py

Directly disable all the stepper motors on a global motor_off() from
the StepperEnable() class in stepper_enable.py.  This simplifies the
toolhead and kinematic classes.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/kinematics/delta.py

@@ -23,6 +23,8 @@ class DeltaKinematics:
             stepper_configs[2], need_position_minmax = False,
             default_position_endstop=a_endstop)
         self.rails = [rail_a, rail_b, rail_c]
+        config.get_printer().register_event_handler("stepper_enable:motor_off",
+                                                    self._motor_off)
         # Setup stepper max halt velocity
         self.max_velocity, self.max_accel = toolhead.get_max_velocity()
         self.max_z_velocity = config.getfloat(
@@ -105,10 +107,8 @@ class DeltaKinematics:
         forcepos = list(self.home_position)
         forcepos[2] = -1.5 * math.sqrt(max(self.arm2)-self.max_xy2)
         homing_state.home_rails(self.rails, forcepos, self.home_position)
-    def motor_off(self, print_time):
+    def _motor_off(self, print_time):
         self.limit_xy2 = -1.
-        for rail in self.rails:
-            rail.motor_enable(print_time, 0)
         self.need_home = True
     def check_move(self, move):
         end_pos = move.end_pos