charger-manager: Provide cm_notify_event function for in-kernel use

By using cm_notify_event function, charger driver can report several
charger events (e.g. battery full and external power in/out, etc) to
Charger-Manager. Charger-Manager can properly and immediately control
chargers by the reported event.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Donggeun Kim <dg77.kim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>