dt-bindings: Add vendor prefix for MaxBotix

Add MaxBotix, which is a vendor of ultrasonic rangers in different
varieties and interfaces.

Signed-off-by: Andreas Klinger <ak@it-klinger.de>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>