libsensors: Added support for Proximity sensor

libsensors: Added support for Proximity sensor

This patch adds the HAL specific changes for Proximity Sensor.
This uses IIO model to communicate to kernel driver.

Change-Id: I1f34f1530b3182dc78d22bf486aa3600b0c7ec23
Signed-off-by: Archana Patni <archana.patni@intel.com>
Reviewed-on: https://android.intel.com/162360
Tested-by: sys_abtbuild <sys_abtbuild@intel.com>
Reviewed-by: Persson, Per <per.persson@intel.com>
Reviewed-by: Sesha, Subramony <subramony.sesha@intel.com>
Reviewed-by: Lilja, Ola <ola.lilja@intel.com>