intel_mid_umip: Sysfs Interface for the USB Host Enable UMIP value

intel_mid_umip: Sysfs Interface for the USB Host Enable UMIP value

BZ:13299

Added functionality to expose the USB Host Enable UMIP value in
sysfs. We can read the current value and modify the existing value
by writing to the sysfs interface.

Usage:

cd /sys/devices/platform/intel_mid_umip

To list the available timeouts
===========
cat available_timeouts

To list the current programmed timeout
===================
cat current_timeout

To change the current programmed timeout
===================
echo <timeout> >  current_timeout

Change-Id: Ia8a43f85388beeb2b644bffd16d0374457af36e3
Signed-off-by: Surya P Sahukar <surya.p.sahukar@intel.com>
Signed-off-by: Hari K Kanigeri <harik.k.kanigeri@intel.com>
Reviewed-on: http://android.intel.com:8080/31586
Reviewed-by: Yang, Fei <fei.yang@intel.com>
Reviewed-by: Kuppuswamy, Sathyanarayanan <sathyanarayanan.kuppuswamy@intel.com>
Reviewed-by: Dong, Chuanxiao <chuanxiao.dong@intel.com>
Tested-by: Sun, Jianhua <jianhua.sun@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>