dt-bindings: hwmon: Add TMP512/513

Document the TMP513/512 device devicetree bindings

Signed-off-by: Eric Tremblay <etremblay@distech-controls.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20191112223001.20844-2-etremblay@distech-controls.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>