dt-bindings: iio: temperature: Add DT bindings for TMP117

Add devicetree binding document for TMP117, a digital temperature sensor.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210407182147.77221-2-puranjay12@gmail.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>