iio: light: tcs3472: add link to datasheet

Add a link to the TCS3472 datasheet in the AMS's website.

Cc: Peter Meerwald <pmeerw@pmeerw.net>
Cc: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/light/tcs3472.c

@@ -11,6 +11,8 @@
  * 7-bit I2C slave address 0x39 (TCS34721, TCS34723) or 0x29 (TCS34725,
  * TCS34727)
  *
+ * Datasheet: http://ams.com/eng/content/download/319364/1117183/file/TCS3472_Datasheet_EN_v2.pdf
+ *
  * TODO: interrupt support, thresholds, wait time
  */