ACPI / PM: Fix problems with acpi_pm_device_sleep_state()

There is a number of problems with acpi_pm_device_sleep_state() now.
First, if _S0W is not defined, it prevents devices from being put
into D3 by PCI runtime PM, which shouldn't happen.  Second, it
shouldn't use adev->wakeup.state.enabled, because if it's set, it
only means that either the device is permanently enabled to wake up
the system, or that it has been enabled to do that through
/proc/acpi/wakeup.  Finally, it should be compiled if CONFIG_PM_SLEEP
is not set, so that PCI runtime PM works correctly in that case.
Fix these problems.

Reported-by: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>