power_supply: allow power supply devices registered w/o wakeup source

Currently, all the power supply devices are registered with wakeup source,
this results in that every power_supply_changed() invocation brings
the system out of suspend-to-freeze state.

This is overkill as some device drivers, e.g. ACPI battery driver,
have the ability to check the device status and wake up the system
from sleeping only when necessary.

Thus introduce a new API which allows device to be registered
w/o wakeup source.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>