xen: arm: Import of_bus PCI entry from Linux (as a dt_bus entry)

xen: arm: Import of_bus PCI entry from Linux (as a dt_bus entry)

This provides specific handlers for the PCI bus relating to matching
and translating. It's mostly similar to the defaults but includes some
additional error checks and other PCI specific bits.

There are some subtle differences in how the generic code vs. the pci
specific code here will handle buggy DTs (i.e. #*-cells which are not
as required by the pci bindings). This will mean we tolerate such
device trees better.

I say "buggy", but actually it's not clear to me from reading "PCI Bus
Binding to Open Firmware" that when the device_type is "pci" that
e.g. the text says "The value of "#address-cells" for PCI Bus Nodes is
3." and not "A PCI Bus Node must contain a #address-cells property
containing 3", iow the #address-cells might validly be implicit rather
than an actual property. Maybe that interpretation is bogus, but with
this patch we are are able to cope with DTs written by people who do
read it like that.

It also gets us the ability to parse the flags (cacheability),
although at the moment we only check them for validity rather than use
them.

Functions/types renamed and reindented (because apparently we do
that for these).

Needs a selection of IORESOURCE_* defines, which I've taken from Linux
and have included locally for now until we figure out where else they
might be needed.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Julien Grall <julien.grall@citrix.com>