creating PCI-related sysfs entries

[Benjamin Herrenschmidt]

> That's only because your arch might happen to have 1 device per slot,
> which is not true for other arches.  And I bet it's also not true for
> your non-virtual boxes...

Even that is not true since we can have multi-function devices or
devices with p2p bridges but the basic entity where the error management
infos is available to us is indeed the physical slot.

> People have suggested that they create such a driver for a long time.
> Why not just do that?

Depends if he wants per domain statistics or really per slot ... we do
have per-slot control on most of IBM machines, thus I would rather have
these info there (though if he also wants consolidated "global" stats,
then yes, a host controller driver might be the way to go).