dt-bindings: Add ti,tmp125 temperature sensor binding

From the freely available Texas Instruments' TMP125 datasheet:

"The TMP125 is an SPI-compatible temperature sensor available in the
tiny SOT23-6 package. Requiring no external components, the TMP125
is capable of measuring temperatures within 2 degree C of accuracy
over a temperature range of −25 degree C to +85 degree C and
2.5 degree C of accuracy over −40 degree C to +125 degree C."

The TMP125 is very similar to the TMP121/TMP122 series of familiar
chips.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/d3538ba9beededfe3a9ad5dab4903a6a01834822.1645175187.git.chunkeey@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>