tmc2660: Add vsense_resistor config parameter

Signed-off-by: Florian Heilmann <Florian.Heilmann@gmx.net>

config/example-extras.cfg

@@ -1050,6 +1050,9 @@
 #run_current:
 #   The amount of current (in ampere) used by the driver during stepper
 #   movement. This parameter must be provided.
+#sense_resistor: 0.051
+#   The resistance (in ohms) of the motor sense resistor. The default
+#   is 0.051 ohms.
 #idle_current_percent: 100
 #   The percentage of the run_current the stepper driver will be
 #   lowered to when the idle timeout expires (you need to set up the