power: supply: act8945a_charger: Achieve properties from its node

Since the act8945a_charger is regarded as a sub-device, all properties will
be assigned to its own device node. All properties can be achieved from its
own node, instead of from its parent device.

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