power: supply: act8945a_charger: Improve state handling

When get the property, first check the charger state machine,
then check the status bit to decide what value is assigned to
the corresponding property.

Retain the SUSCHG bit of REG 0x71 when configure the timers to
avoid losting the charger suspending info after boot.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>