ACPI / PM: Make acpi_pm_device_sleep_state() follow the specification

The comparison between the system sleep state being entered
and the lowest system sleep state the given device may wake up
from in acpi_pm_device_sleep_state() is reversed, because the
specification (ACPI 5.0) says that for wakeup to work:

"The sleeping state being entered must be less than or equal to the
 power state declared in element 1 of the _PRW object."

In other words, the state returned by _PRW is the deepest
(lowest-power) system sleep state the device is capable of waking up
the system from.

Moreover, acpi_pm_device_sleep_state() also should check if the
wakeup capability is supported through ACPI, because in principle it
may be done via native PCIe PME, for example, in which case _SxW
should not be evaluated.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

drivers/acpi/sleep.c

@@ -773,8 +773,8 @@ int acpi_pm_device_sleep_state(struct device *dev, int *d_min_p)
 	 * can wake the system.  _S0W may be valid, too.
 	 */
 	if (acpi_target_sleep_state == ACPI_STATE_S0 ||
-	    (device_may_wakeup(dev) &&
-	     adev->wakeup.sleep_state <= acpi_target_sleep_state)) {
+	    (device_may_wakeup(dev) && adev->wakeup.flags.valid &&
+	     adev->wakeup.sleep_state >= acpi_target_sleep_state)) {
 		acpi_status status;
 
 		acpi_method[3] = 'W';