PCI: Mark invalid BARs as unassigned

If a BAR is not inside any upstream bridge window, or if it conflicts with
another resource, mark it as IORESOURCE_UNSET so we don't try to use it.
We may be able to assign a different address for it.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>