config: Move description of phase adjusted endstops to config-extra.cfg

Move the description of stepper phase adjusted endstops to a new
section in config-extra.cfg.  This keeps the main example config file
a little more concise.

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

config/example-extras.cfg

@@ -116,6 +116,35 @@
 #   axis is triggered.
 
 
+# Stepper phase adjusted endstops. The following additional parameters
+# may be added to a stepper axis definition to improve the accuracy of
+# endstop switches.
+#[stepper_z]
+#homing_stepper_phases:
+#   One may set this to the number of phases of the stepper motor
+#   driver (which is the number of micro-steps multiplied by
+#   four). This parameter must be provided if using stepper phase
+#   adjustments.
+#homing_endstop_accuracy: 0.200
+#   Sets the expected accuracy (in mm) of the endstop. This represents
+#   the maximum error distance the endstop may trigger (eg, if an
+#   endstop may occasionally trigger 100um early or up to 100um late
+#   then set this to 0.200 for 200um). The default is
+#   homing_stepper_phases*step_distance.
+#homing_endstop_phase:
+#   This specifies the phase of the stepper motor driver to expect
+#   when hitting the endstop. Only set this value if one is sure the
+#   stepper motor driver is reset every time the mcu is reset. If this
+#   is not set, then the stepper phase will be detected on the first
+#   home and that phase will be used on all subsequent homes.
+#homing_endstop_align_zero: False
+#   If true then the code will arrange for the zero position on the
+#   axis to occur at a full step on the stepper motor. (If used on the
+#   Z axis and the print layer height is a multiple of a full step
+#   distance then every layer will occur on a full step.) The default
+#   is False.
+
+
 # Heater cooling fans (one may define any number of sections with a
 # "heater_fan" prefix). A "heater fan" is a fan that will be enabled
 # whenever its associated heater is active. In the event of an MCU