Minor clean up to CPU setup - use smp_processor_id instead of custom hack

Does not change any semantics because numa_add_cpu checks for CPU 0 
anyways.

Index: linux/arch/x86_64/kernel/setup.c
===================================================================
--- linux.orig/arch/x86_64/kernel/setup.c
+++ linux/arch/x86_64/kernel/setup.c
@@ -1081,8 +1079,7 @@ void __cpuinit identify_cpu(struct cpuin
 	else
 		mtrr_ap_init();
 #ifdef CONFIG_NUMA
-	if (c != &boot_cpu_data)
-		numa_add_cpu(c - cpu_data);
+	numa_add_cpu(smp_processor_id());
 #endif
 }