iio: Add driver for AMS/TAOS tcs3414 digital color sensor

16-bit digital color sensor with red, green, blue and clear channel

datasheet: http://ams.com/eng/content/download/250258/975997/TCS3414_Datasheet_EN_v1.pdf



Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>