power: charger-manager: Use alarmtimer for battery monitoring in suspend.

To guerantee proper charing and managing batteries even in suspend,
charger-manager has used rtc device with rtc framework interface.
However, it is better to use alarmtimer for cleaner and more appropriate
operation.
This patch makes driver to use alarmtimer for polling work in suspend and
removes all deprecated codes related with using rtc interface.

Signed-off-by: Jonghwa Lee <jonghwa3.lee@samsung.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>