ACPI / PM: Do not execute _PS0 for devices without _PSC during initialization

Commit b3785492 (ACPI / PM: Do not power manage devices in unknown
initial states) added code to force devices without _PSC, but having
_PS0 defined in the ACPI namespace, into ACPI power state D0 by
executing _PS0 for them.  That turned out to break Toshiba P870-303,
however, so revert that code.

References: https://bugzilla.kernel.org/show_bug.cgi?id=58201Reported-and-tested-by: Jerome Cantenot <jerome.cantenot@gmail.com>
Tracked-down-by: Lan Tianyu <tianyu.lan@intel.com>
Cc: 3.9+ <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/device_pm.c

@@ -278,11 +278,13 @@ int acpi_bus_init_power(struct acpi_device *device)
 		if (result)
 			return result;
 	} else if (state == ACPI_STATE_UNKNOWN) {
-		/* No power resources and missing _PSC? Try to force D0. */
+		/*
+		 * No power resources and missing _PSC?  Cross fingers and make
+		 * it D0 in hope that this is what the BIOS put the device into.
+		 * [We tried to force D0 here by executing _PS0, but that broke
+		 * Toshiba P870-303 in a nasty way.]
+		 */
 		state = ACPI_STATE_D0;
-		result = acpi_dev_pm_explicit_set(device, state);
-		if (result)
-			return result;
 	}
 	device->power.state = state;
 	return 0;