PCI: Expand "VPD access disabled" quirk message

It's not very enlightening to see

  pci 0000:07:00.0: [Firmware Bug]: VPD access disabled

in the dmesg log because there's no clue about what the firmware bug is.
Expand the message to explain why we're disabling VPD.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/quirks.c

@@ -2156,7 +2156,7 @@ static void quirk_blacklist_vpd(struct pci_dev *dev)
 {
 	if (dev->vpd) {
 		dev->vpd->len = 0;
-		dev_warn(&dev->dev, FW_BUG "VPD access disabled\n");
+		dev_warn(&dev->dev, FW_BUG "disabling VPD access (can't determine size of non-standard VPD format)\n");
 	}
 }