This patch pulls the PCI-related junk out of struct device_node and
puts it in a separate structure, struct pci_dn.  The device_node now
just has a void * pointer in it, which points to a struct pci_dn for
nodes that represent PCI devices.  It could potentially be used in
future for device-specific data for other sorts of devices, such as
virtual I/O devices.

Signed-off-by: Paul Mackerras <paulus@samba.org>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!