PCI: Fix unaligned access in AF transaction pending test

pci_wait_for_pending() uses word access, so we shouldn't be passing
an offset that is only byte aligned.  Use the control register offset
instead, shifting the mask to match.

Fixes: d0b4cc4e32 ("PCI: Wrong register used to check pending traffic")
Fixes: 157e876ffe ("PCI: Add pci_wait_for_pending() (refactor pci_wait_for_pending_transaction())
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
CC: stable@vger.kernel.org	# v3.14+

drivers/pci/pci.c

@@ -3135,8 +3135,13 @@ static int pci_af_flr(struct pci_dev *dev, int probe)
 	if (probe)
 		return 0;
 
-	/* Wait for Transaction Pending bit clean */
-	if (pci_wait_for_pending(dev, pos + PCI_AF_STATUS, PCI_AF_STATUS_TP))
+	/*
+	 * Wait for Transaction Pending bit to clear.  A word-aligned test
+	 * is used, so we use the conrol offset rather than status and shift
+	 * the test bit to match.
+	 */
+	if (pci_wait_for_pending(dev, pos + PCI_AF_CTRL,
+				 PCI_AF_STATUS_TP << 8))
 		goto clear;
 
 	dev_err(&dev->dev, "transaction is not cleared; proceeding with reset anyway\n");