dt-bindings: iio: light: add ltr390

Add binding for Lite-On LTR390 which is an Ambient/UV light sensor that
communicates over i2c with an address of 0x53.

Datasheet: https://optoelectronics.liteon.com/upload/download/DS86-2015-0004/LTR-390UV_Final_%20DS_V1%201.pdf


Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Anshul Dalal <anshulusr@gmail.com>
Link: https://lore.kernel.org/r/20231208102211.413019-1-anshulusr@gmail.com


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