Charger: Add a Charger to Android transition threshold

Existing code allows charger-mode to exit to Android even with 0%
battery.
This might lead to more battery discharge while booting to Android,
especially if only USB-charger is connected, and thus certain
features/components not functioning as expected in Android.

This patch adds a configurable parameter to improve the user experience
by preventing the charger exit till battery capacity is good enough to
boot Android

Change-Id: I56a283243551373e962ac562f25eaf11f07666c3
Signed-off-by: Pavan Kumar S <pavan.kumar.s@intel.com>
Signed-off-by: Jenny TC <jenny.tc@intel.com>
Signed-off-by: Yong Yao <yong.yao@intel.com>