grove: add light sensor

Add driver for the Grove Light Sensor which detects changes in ambient light.

Sensor reference page:
	http://www.seeedstudio.com/wiki/Grove_-_Light_Sensor



Origin: Original
Change-Id: I88ae20cc9faa8ab8f274b0bd7a114db5c1a87a91
Signed-off-by: Bogdan Davidoaia <bogdan.m.davidoaia@intel.com>