[IA64] Make SN2 PCI code use ioremap rather than manually mangle the address

This one changes the SN2 specific PCI drivers to use ioremap() for
obtaining the real address to access for the PCI registers instead of
manually calculating them with __IA64_UNCACHED_OFFSET.

The patch should have no real change when running on a normal Linux
kernel, but when running as a paravirtualized it is needed.

Signed-off-by: Jes Sorenson <jes@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>