pci: Add generic pcibios_{fixup_bus,align_resource}

[Bjorn Helgaas]

On Fri, Jun 23, 2017 at 06:50:41PM -0700, Palmer Dabbelt wrote:
> While upstreaming the RISC-V port, it was pointed out that multiple
> architectures have copied the mostly empty versions of at least one of these
> functions.  This defines weakly bound versions of the common functions and
> removes the now obselete functions from other ports.
> 
> This has been split out from the RISC-V submission so we can decouple all these
> generic changes from our port review process.  There's some discussion on an
> earlier version of the patch here
> 
>   https://lkml.org/lkml/2017/6/6/998
> 
> but I'm afraid a lot of this is really out of my wheelhouse (and I'm pretty
> slammed trying to get the RISC-V port in better shape), so I'm afraid I'm not
> going to be able to perform the full cleanup suggested.

Applied to pci/resource for v4.14, thanks!

There's room for future improvement, e.g., using per-host callbacks,
etc., but I think this is a clear improvement as-is.

There's some folklore about the evils of weak symbols, but I don't
know the details.  It would be useful to have them codified somewhere
in Documentation/ or near the __weak definition.