Add initial support for ltrf216a ambient light sensor.

Datasheet: https://gitlab.collabora.com/shreeya/iio/-/blob/master/LTRF216A.pdfReviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Co-developed-by: Zhigang Shi <Zhigang.Shi@liteon.com>
Signed-off-by: Zhigang Shi <Zhigang.Shi@liteon.com>
Co-developed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Shreeya Patel <shreeya.patel@collabora.com>
Link: https://lore.kernel.org/r/20220725104050.491396-3-shreeya.patel@collabora.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>