ACPI: Add _PLD support

Add a simple helper function to allow drivers to obtain the physical
device location data.

Acked-by: Len Brown <len.brown@intel.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>