QOL Motor name force convert to lowercase

[Obscured84]

Not an issue, Just a bit of improvement (maybe I'm wrong)
forcing lowercase in motor name

Makes it easier to copy & paste motor names from datasheets

AutotuneTMC config parameters

    self.motor = config.get('motor').lower()
    self.motor_name = "motor_constants " + self.motor
    try:
        motor = self.printer.lookup_object(self.motor_name)

[Obscured84]

created pull request QOL- forcing lowercase when reading motorname from config