iio_sensors: Add Light sensor sysfs interface and transformation

iio_sensors: Add Light sensor sysfs interface and transformation

The IIO/HID sensor hub driver publishes the light sensor data using the
IIO_INTENSITY defined in iio industrial-core. This patch adds this
sensor type to the sensor catalogue and adds a corresponding transformation
in transform_sample_ISH function.

This was tested on BDW Wilson Beach (running Intel FW) and on BDW RVP Y
(running STM FW).

Change-Id: Ib0629dca03f8ec645fcd4d5816ee7131e1764e39
Signed-off-by: Archana Patni <archana.patni@intel.com>
Signed-off-by: Subramony Sesha <subramony.sesha@intel.com>