iio: jsa1212: Add JSA1212 proximity/ALS sensor

This patch adds a new driver for solteam opto JSA1212 proximity and
ambient light sensor.

Basic details of the chip can be found here.

http://www.solteamopto.com.tw/detail.php?ms=3&po_unit=2&pt_unit=29&p_unit=120



Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>