[IA64] hotplug/ia64: SN Hotplug Driver: moving of header files

This patch moves header files out of the arch/ia64/sn directories and into
include/asm-ia64/sn.  These files were being included by other subsystems
and should be under include/asm-ia64/sn.

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