PCI/PME: Restructure pcie_pme_suspend() to prevent compiler warning

Previously we had this:

  if (wakeup)
    ret = enable_irq_wake(...);
  if (!wakeup || ret)
    ...

"ret" is only evaluated when "wakeup" is true, and it is always initialized
in that case, but gcc isn't smart enough to figure that out and warns:

  drivers/pci/pcie/pme.c:414:14: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]

Restructure the code slightly to make it easier for gcc (and maybe for
humans as well).
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com

drivers/pci/pcie/pme.c

@@ -396,7 +396,7 @@ static int pcie_pme_suspend(struct pcie_device *srv)
 {
 	struct pcie_pme_service_data *data = get_service_data(srv);
 	struct pci_dev *port = srv->port;
-	bool wakeup;
+	bool wakeup, wake_irq_enabled = false;
 	int ret;
 
 	if (device_may_wakeup(&port->dev)) {
@@ -409,9 +409,12 @@ static int pcie_pme_suspend(struct pcie_device *srv)
 	spin_lock_irq(&data->lock);
 	if (wakeup) {
 		ret = enable_irq_wake(srv->irq);
+		if (ret == 0) {
 			data->suspend_level = PME_SUSPEND_WAKEUP;
+			wake_irq_enabled = true;
 		}
-	if (!wakeup || ret) {
+	}
+	if (!wake_irq_enabled) {
 		pcie_pme_interrupt_enable(port, false);
 		pcie_clear_root_pme_status(port);
 		data->suspend_level = PME_SUSPEND_NOIRQ;