dt-bindings: Add TI LM73 as a trivial device

The Texas Instruments LM73 is a digital temperature sensor with 2-wire
interface. Add LM73 as a trivial device.

Signed-off-by: Henry Shen <henry.shen@alliedtelesis.co.nz>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200212030615.28537-2-henry.shen@alliedtelesis.co.nz


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