PCI: acpiphp: check whether _ADR evaluation succeeded

commit dfb117b3e50c52c7b3416db4a4569224b8db80bb upstream.

Check whether we evaluated _ADR successfully.  Previously we ignored
failure, so we would have used garbage data from the stack as the device
and function number.

We return AE_OK so that we ignore only this slot and continue looking
for other slots.

Found by Coverity (CID 113981).

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>