dt-bindings: hwmon: adi,ltc2945: Add binding

Create initial binding for the LTC2945 I2C power monitor.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Jonathan Cormier <jcormier@criticallink.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>