power_supply: Add support for CHARGE_CONTROL_* attributes

Add support for power supply attributes CHARGE_CONTROL_LIMIT
and CHARGE_CONTROL_LIMIT_MAX.

These new attributes will enable the user space to implement
custom charging algorithms based on platform state.

Signed-off-by: Ramakrishna Pallala <ramakrishna.pallala@intel.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>