ACPI: acpi_pci_set_power_state() cleanups

Minor cleanups to acpi_pci_set_power_state():  use the ACPI and PCI
state symbols to make clear that a mapping is being done between PCI
and ACPI states, instead of using magic numbers.  For paranoia's sake,
report any errors.  Save five bytes (x86_64) too.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/pci/pci-acpi.c

@@ -272,21 +272,29 @@ static int acpi_pci_set_power_state(struct pci_dev *dev, pci_power_t state)
 {
 	acpi_handle handle = DEVICE_ACPI_HANDLE(&dev->dev);
 	acpi_handle tmp;
-	static int state_conv[] = {
-		[0] = 0,
-		[1] = 1,
-		[2] = 2,
-		[3] = 3,
-		[4] = 3
+	static const u8 state_conv[] = {
+		[PCI_D0] = ACPI_STATE_D0,
+		[PCI_D1] = ACPI_STATE_D1,
+		[PCI_D2] = ACPI_STATE_D2,
+		[PCI_D3hot] = ACPI_STATE_D3,
+		[PCI_D3cold] = ACPI_STATE_D3
 	};
-	int acpi_state = state_conv[(int __force) state];
 
 	if (!handle)
 		return -ENODEV;
 	/* If the ACPI device has _EJ0, ignore the device */
 	if (ACPI_SUCCESS(acpi_get_handle(handle, "_EJ0", &tmp)))
 		return 0;
-	return acpi_bus_set_power(handle, acpi_state);
+
+	switch (state) {
+	case PCI_D0:
+	case PCI_D1:
+	case PCI_D2:
+	case PCI_D3hot:
+	case PCI_D3cold:
+		return acpi_bus_set_power(handle, state_conv[state]);
+	}
+	return -EINVAL;
 }