It's possible to have buses without an associated bridge
(bus->self == NULL). SR-IOV can generate such buses. When
we find these, skip to the parent bus to look for the next
ACS test.
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---
David Ahern reported an oops from iommu drivers passing NULL into
this function for the same mistake. Harden this function against
assuming bus->self is valid as well. David, please include this
patch as well as the iommu patches in your testing.