ACPI/PCI: Reorder checks in acpi_pci_osc_control_set()

Make acpi_pci_osc_control_set() attempt to find the handle of the
_OSC object under the given PCI root bridge object after verifying
that its second argument is correct and that there is a struct
acpi_pci_root object for the given root bridge handle, which is
more logical than the old code.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/acpi/pci_root.c

@@ -378,10 +378,6 @@ acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 flags)
 	acpi_handle tmp;
 	struct acpi_pci_root *root;
 
-	status = acpi_get_handle(handle, "_OSC", &tmp);
-	if (ACPI_FAILURE(status))
-		return status;
-
 	control_req = (flags & OSC_PCI_CONTROL_MASKS);
 	if (!control_req)
 		return AE_TYPE;
@@ -390,6 +386,10 @@ acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 flags)
 	if (!root)
 		return AE_NOT_EXIST;
 
+	status = acpi_get_handle(handle, "_OSC", &tmp);
+	if (ACPI_FAILURE(status))
+		return status;
+
 	mutex_lock(&osc_lock);
 	/* No need to evaluate _OSC if the control was already granted. */
 	if ((root->osc_control_set & control_req) == control_req)