An upstream bridge's I/O window must be at least as aligned as any
downstream device or bridge requires.  In particular, if the upstream
bridge supports 1K alignment but a downstream bridge requires 4K alignment,
the upstream window must also be 4K aligned.

Therefore, do not reduce the required alignment ("min_align") based on
the upstream bridge's capabilities.
Reported-by: NWei Yang <weiyang@linux.vnet.ibm.com>
Suggested-by: NYinghai Lu <yinghai@kernel.org>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>