[IA64] Fix typo/thinko in arch/ia64/sn/kernel/sn2/sn2_smp.c

sn2_ptc_init() has what looks like a cut-n-paste error. Fix it.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>