dt-bindings: maxbotix,mb1232: Add MaxBotix i2c ultrasonic rangers

Add doc for dt binding maxbotix,mb1232. This binding is for MaxBotix
I2CXL-MaxSonar ultrasonic rangers which share a common i2c interface.

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