PCI: Short-circuit pci_device_is_present() for disconnected devices

If the PCI device is disconnected, return false immediately from
pci_device_is_present().  pci_device_is_present() uses the bus accessors,
so the early return in the device accessors doesn't help here.
Tested-by: NKrishna Dhulipala <krishnad@fb.com>
Signed-off-by: NKeith Busch <keith.busch@intel.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NWei Zhang <wzhang@fb.com>

drivers/pci/pci.c

@@ -4932,6 +4932,8 @@ bool pci_device_is_present(struct pci_dev *pdev)
 {
 	u32 v;
 
+	if (pci_dev_is_disconnected(pdev))
+		return false;
 	return pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v, 0);
 }
 EXPORT_SYMBOL_GPL(pci_device_is_present);