stepper: Use config.getlists() for gear_ratio config option

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

klippy/stepper.py

@@ -215,17 +215,11 @@ def PrinterStepper(config, units_in_radians=False):
 
 # Parse stepper gear_ratio config parameter
 def parse_gear_ratio(config, note_valid):
-    gear_ratio = config.get('gear_ratio', None, note_valid=note_valid)
-    if gear_ratio is None:
-        return 1.
+    gear_ratio = config.getlists('gear_ratio', (), seps=(':', ','), count=2,
+                                 parser=float, note_valid=note_valid)
     result = 1.
-    try:
-        gears = gear_ratio.split(',')
-        for gear in gears:
-            g1, g2 = [float(v.strip()) for v in gear.split(':')]
+    for g1, g2 in gear_ratio:
         result *= g1 / g2
-    except:
-        raise config.error("Unable to parse gear_ratio: %s" % (gear_ratio,))
     return result
 
 # Obtain "step distance" information from a config section