x86: convert to generic helpers for IPI function calls

This converts x86, x86-64, and xen to use the new helpers for
smp_call_function() and friends, and adds support for
smp_call_function_single().

Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/include/asm-x86/hw_irq_32.h b/include/asm-x86/hw_irq_32.h
index ea88054..a87b132 100644
--- a/include/asm-x86/hw_irq_32.h
+++ b/include/asm-x86/hw_irq_32.h
@@ -32,6 +32,7 @@
 void reschedule_interrupt(void);
 void invalidate_interrupt(void);
 void call_function_interrupt(void);
+void call_function_single_interrupt(void);
 #endif
 
 #ifdef CONFIG_X86_LOCAL_APIC