libata: handle pci_enable_device() failure while resuming

Handle pci_enable_device() failure while resuming.  This patch kills
the "ignoring return value of 'pci_enable_device'" warning message and
propagates __must_check through ata_pci_device_do_resume().

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index ca53d5a..03b7a005 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1397,7 +1397,9 @@
 	void __iomem *mmio = host->mmio_base;
 	int rc;
 
-	ata_pci_device_do_resume(pdev);
+	rc = ata_pci_device_do_resume(pdev);
+	if (rc)
+		return rc;
 
 	if (pdev->dev.power.power_state.event == PM_EVENT_SUSPEND) {
 		rc = ahci_reset_controller(mmio, pdev);