ACPI: acpi_pad: Still evaluate _OST when _PUR evaluation fails

The ACPI specification says that if no action was performed when
processing the _PUR object, _OST should still be evaluated, albeit
with a different status code.

Evaluate _OST even when evaluating _PUR fails, to signal the firmware
that no action was performed.

Compile-tested only.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>