homing: Handle speed rounding when homing speed greater than max_velocity

Commit 002dc0df added rounding to the homing speed, but it did not
work if the configured homing speed was less than the printer's
maximum velocity.  Move the speed rounding from stepper.py to
homing.py and make sure the rounded speed is less than the maximum
speed.

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

klippy/stepper.py

@@ -122,13 +122,6 @@ class PrinterHomingStepper(PrinterStepper):
                 self.homing_endstop_accuracy = self.homing_stepper_phases
     def get_endstops(self):
         return [(self.mcu_endstop, self.name)]
-    def get_homing_speed(self):
-        # Round the configured homing speed so that it is an even
-        # number of ticks per step.
-        adjusted_freq = self.mcu_stepper.get_mcu().get_adjusted_freq()
-        dist_ticks = adjusted_freq * self.step_dist
-        ticks_per_step = round(dist_ticks / self.homing_speed)
-        return dist_ticks / ticks_per_step
     def get_homed_offset(self):
         if not self.homing_stepper_phases or self.need_motor_enable:
             return 0.