[IA64] hotplug/ia64: SN Hotplug Driver - SN Hotplug Driver code

This patch is the SGI hotplug driver and additional changes required for
the driver.  These modifications include changes to the SN io_init.c code
for memory management, the inclusion of new SAL calls to enable and disable
PCI slots, and a hotplug-style driver.

Signed-off-by: Prarit Bhargava <prarit@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>