iio: light: ROHM BU27008 color sensor

iio: light: ROHM BU27008 color sensor

The ROHM BU27008 is a sensor with 5 photodiodes (red, green, blue, clear
and IR) with four configurable channels. Red and green being always
available and two out of the rest three (blue, clear, IR) can be
selected to be simultaneously measured. Typical application is adjusting
LCD backlight of TVs, mobile phones and tablet PCs.

Add initial support for the ROHM BU27008 color sensor.
 - raw_read() of RGB and clear channels
 - triggered buffer w/ DRDY interrtupt

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Link: https://lore.kernel.org/r/2594162f0e44148cffb1fb05f1d6edfde6bd11bc.1683541225.git.mazziesaccount@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>