Add function acpi_bus_init_power() for getting the initial power
state of an ACPI device and reference counting its power resources
as appropriate.

Make acpi_bus_get_power_flags() use the new function instead of
acpi_bus_get_power() that updates device->power.state without
reference counting the device's power resources.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: NLen Brown <len.brown@intel.com>