power: charger-manager: Support to change polling rate in runtime.

power: charger-manager: Support to change polling rate in runtime.

Add 'polling_ms' sysfs node to change charger-manager's monitoring rate
in runtime. It can set only bigger than 2 jiffies (for 200 HZ system it
is 10 msecs.) as it's allowed for minimum poling rate in previous.
It resets poller and re-configure polling rate based on new input if next
polling time is far enough. Otherwise, it just waits expiration of timer
and new polling rate will affects the next scheduling.

Change-Id: I6a9a07b96db2554e2ec047224df818dcc4ab1a17
Signed-off-by: Jonghwa Lee <jonghwa3.lee@samsung.com>