x86: separate generic cpu disabling code from APIC writes in cpu_disable

It allows paravirt implementations of cpu_disable to share the
cpu_disable_common code, without having to take on board APIC
writes, which may not be appropriate.

Signed-off-by: Alex Nixon <alex.nixon@citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/asm-x86/smp.h b/include/asm-x86/smp.h
index 17305e72..8bdaa4a 100644
--- a/include/asm-x86/smp.h
+++ b/include/asm-x86/smp.h
@@ -125,6 +125,7 @@
 	smp_ops.send_call_func_ipi(mask);
 }
 
+void cpu_disable_common(void);
 void native_smp_prepare_boot_cpu(void);
 void native_smp_prepare_cpus(unsigned int max_cpus);
 void native_smp_cpus_done(unsigned int max_cpus);