pci-OF-bus-map deprecation

For 32 bits machines with Open Firmware, we used to create a
pci-OF-bus-map property in the device-tree that provided a mapping
between linux and Open Firmware PCI bus numbers (since on some platforms
like PowerMac, we still renumber PCI busses).

This property is no longer necessary as

 - Nowadays, we have sysfs and the PCI devices in there do have a full
Open Firmware device path exposed as a "devspec" file in their sysfs
directories
 - I don't think anybody ever used that property in userland :)

This mail is mostly to make sure of the later. I intend to get rid of it
in 2.6.18 (that's early, but as I said, I think nobody uses it anyway. I
intended to use it in some X stuff I never ended up actually
implementing...)

It only concerns 32 bits ppc machines with OF, and only the ones that
renumber busses, which means basically only PowerMacs.

Ben.