PCI: Fix disable IRQ 0 in pci_reset_function()

Before initialization, dev->irq may be zero. Make sure we don't disable
it at reset time in that case.
Reviewed-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/pci.c

@@ -1832,7 +1832,7 @@ int pci_reset_function(struct pci_dev *dev)
 	if (!(cap & PCI_EXP_DEVCAP_FLR))
 		return -ENOTTY;
 
-	if (!dev->msi_enabled && !dev->msix_enabled)
+	if (!dev->msi_enabled && !dev->msix_enabled && dev->irq != 0)
 		disable_irq(dev->irq);
 	pci_save_state(dev);
 
@@ -1841,7 +1841,7 @@ int pci_reset_function(struct pci_dev *dev)
 	r = pci_execute_reset_function(dev);
 
 	pci_restore_state(dev);
-	if (!dev->msi_enabled && !dev->msix_enabled)
+	if (!dev->msi_enabled && !dev->msix_enabled && dev->irq != 0)
 		enable_irq(dev->irq);
 
 	return r;