acpi: bus: handle power manageable but no _PSC/_PRx case

acpi: bus: handle power manageable but no _PSC/_PRx case

Currently, when we are trying to get the power state of an acpi device,
we will do the following:
If device is not power manageable, init its power state as its parent or
if it does not have a parent, init as D0;
If device is power manageable, evaluate _PSC and then refine with
acpi_power_get_inferred_state.

But there exist some devices with _PSx defined, but no _PSC or _PRx.
It is power manageable, but the above method to get power state does
not cover this case and its power state will be UNKNOWN(255).

So change the check of power manageable to whether _PSC and _PRx
defined.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>