x86: move hotplug related extern definitions to smp.h

definitions that are inside CONFIG_HOTPLUG_CPU in
the arch-specific smp*.h files are moved to common
header

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/asm-x86/smp.h b/include/asm-x86/smp.h
index 1b4481a..c800b81 100644
--- a/include/asm-x86/smp.h
+++ b/include/asm-x86/smp.h
@@ -80,6 +80,12 @@
 # include "smp_64.h"
 #endif
 
+#ifdef CONFIG_HOTPLUG_CPU
+extern void cpu_exit_clear(void);
+extern void cpu_uninit(void);
+extern void remove_siblinginfo(int cpu);
+#endif
+
 extern void smp_alloc_memory(void);
 extern void lock_ipi_call_lock(void);
 extern void unlock_ipi_call_lock(void);