PCI: Enable quirks for PCIe ACS on Intel PCH root ports

PCI: Enable quirks for PCIe ACS on Intel PCH root ports

Many of the currently available Intel PCH-based root ports do not provide
PCIe ACS capabilities.  Without this, we must assume that peer-to-peer
traffic between multifunction root ports and between devices behind root
ports is possible.  This lack of isolation is exposed by grouping the
devices together in the same IOMMU group.  If we want to expose these
devices to userspace, vfio uses IOMMU groups as the unit of ownership, thus
making it very difficult to assign individual devices to separate users.

The good news is that the chipset does provide ACS-like isolation
capabilities, but we do need to verify and enable those capabilities if the
BIOS has not done so.  This patch implements the device specific enabling
and testing of equivalent ACS function for these devices.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Don Dugger <donald.d.dugger@intel.com>