[IA64] fix percpu warnings

Fix percpu types warning in ia64/sn:

arch/ia64/sn/kernel/setup.c:74: error: conflicting types for '__pcpu_scope___sn_cnodeid_to_nasid'
arch/ia64/include/asm/sn/arch.h:74: error: previous declaration of '__pcpu_scope___sn_cnodeid_to_nasid' was here

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Jes Sorensen <jes@sgi.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>