PCI / PM: Remove unnecessary error variable from acpi_dev_run_wake()

The result returned by acpi_dev_run_wake() is always either -EINVAL
or -ENODEV, while obviously it should return 0 on success.  The
problem is that the leftover error variable, that's not really used
in the function, is initialized with -ENODEV and then returned
without modification.

To fix this issue remove the error variable from acpi_dev_run_wake()
and make the function return 0 on success as appropriate.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>