iio: Add tcs3472 color light sensor driver

chip has four 16-bit channels for red, green, blue, clear color
intensity; driver supports the TCS3x7x family of devices and was
tested with a TCS34725 chip; further information here:
http://www.ams.com/eng/Products/Light-Sensors/Color-Sensor/TCS34725

v2 (thanks to Jonathan Cameron):
* drop dynamic buffer allocation, buffer is in tcs3472_data
* limit sysfs output to PAGE_SIZE
* check val2 == 0 when writing CALIBSCALE

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Cc: Jon Brenner <jon.brenner@ams.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/light/Kconfig

@@ -55,6 +55,16 @@ config SENSORS_LM3533
 	  changes. The ALS-control output values can be set per zone for the
 	  three current output channels.
 
+config TCS3472
+	tristate "TAOS TCS3472 color light-to-digital converter"
+	depends on I2C
+	help
+	 If you say yes here you get support for the TAOS TCS3472
+	 family of color light-to-digital converters with IR filter.
+
+	 This driver can also be built as a module.  If so, the module
+	 will be called tcs3472.
+
 config SENSORS_TSL2563
 	tristate "TAOS TSL2560, TSL2561, TSL2562 and TSL2563 ambient light sensors"
 	depends on I2C