x86: move prefill_possible_map calling early, fix

fix:

arch/x86/kernel/built-in.o: In function `setup_arch':
: undefined reference to `prefill_possible_map'
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/asm-x86/smp.h

@@ -109,8 +109,6 @@ int native_cpu_up(unsigned int cpunum);
 extern int __cpu_disable(void);
 extern void __cpu_die(unsigned int cpu);
 
-extern void prefill_possible_map(void);
-
 void smp_store_cpu_info(int id);
 #define cpu_physical_id(cpu)	per_cpu(x86_cpu_to_apicid, cpu)
 
@@ -119,11 +117,15 @@ static inline int num_booting_cpus(void)
 {
 	return cpus_weight(cpu_callout_map);
 }
+#endif /* CONFIG_SMP */
+
+#if defined(CONFIG_SMP) && defined(CONFIG_HOTPLUG_CPU)
+extern void prefill_possible_map(void);
 #else
 static inline void prefill_possible_map(void)
 {
 }
-#endif /* CONFIG_SMP */
+#endif
 
 extern unsigned disabled_cpus __cpuinitdata;