charger-manager: Disable regulator when charger cable is detached

This patch disable regulator for charging when charger cable is detached
before stopping charging forcibly on abnormal battery state and check
return value of regulator_enable/disable() function to confirm correct
operation of enabling or disabling regulator for charging.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Myungjoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>