PCI: Add ability to mmap legacy_io on some platforms

This adds the ability to mmap legacy IO space to the legacy_io files
in sysfs on platforms that support it. This will allow to clean up
X to use this instead of /dev/mem for legacy IO accesses such as
those performed by Int10.

While at it I moved pci_create/remove_legacy_files() to pci-sysfs.c
where I think they belong, thus making more things statis in there
and cleaned up some spurrious prototypes in the ia64 pci.h file

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>