PCI: Check IORESOURCE_UNSET before updating BAR

Check to make sure we don't update a BAR with an address we haven't
assigned.

If we haven't assigned an address to a resource, we shouldn't write it to a
BAR.  This isn't a problem for the usual path via pci_assign_resource(),
which clears IORESOURCE_UNSET before calling pci_update_resource(), but
paths like pci_restore_bars() can call this for resources we haven't
assigned.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

drivers/pci/setup-res.c

@@ -44,6 +44,9 @@ void pci_update_resource(struct pci_dev *dev, int resno)
 	if (!res->flags)
 		return;
 
+	if (res->flags & IORESOURCE_UNSET)
+		return;
+
 	/*
 	 * Ignore non-moveable resources.  This might be legacy resources for
 	 * which no functional BAR register exists or another important