Fix acpi_pm_device_sleep_wake() by providing a stub for CONFIG_PM_SLEEP=n

So that one of the several config option permutations will build again.

Tested-by: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>