The Qualcomm QDF2xxx root ports don't advertise an ACS capability, but they
do provide ACS-like features to disable peer transactions and validate bus
numbers in requests.

To be specific:
* Hardware supports source validation but it will report the issue as
Completer Abort instead of ACS Violation.

* Hardware doesn't support peer-to-peer and each root port is a root
complex with unique segment numbers.

* It is not possible for one root port to pass traffic to the other root
port.  All PCIe transactions are terminated inside the root port.

Add an ACS quirk for the QDF2400 and QDF2432 products.

[bhelgaas: changelog]
Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>