[IA64] Prevent sn2 ptc code from executing on all ia64 subarches

Patch to prevent sn2_ptc_init code from attempting to load on non-sn2 systems
when sn2_smp.c is built-in to generic kernel.
Signed-off-by: Prarit Bhargava <prarit@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/sn/kernel/sn2/sn2_smp.c

@@ -492,6 +492,9 @@ static struct proc_dir_entry *proc_sn2_ptc;
 
 static int __init sn2_ptc_init(void)
 {
+	if (!ia64_platform_is("sn2"))
+		return -ENOSYS;
+
 	if (!(proc_sn2_ptc = create_proc_entry(PTC_BASENAME, 0444, NULL))) {
 		printk(KERN_ERR "unable to create %s proc entry", PTC_BASENAME);
 		return -EINVAL;