x86: kill #ifdef for exit_idle()

Impact: cleanup

Introduce helper inline function in arch/x86/include/asm/idle.h
to remove #ifdefs around exit_idle().

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/io_apic.c b/arch/x86/kernel/io_apic.c
index 9043251..679e7bb 100644
--- a/arch/x86/kernel/io_apic.c
+++ b/arch/x86/kernel/io_apic.c
@@ -2216,10 +2216,9 @@
 asmlinkage void smp_irq_move_cleanup_interrupt(void)
 {
 	unsigned vector, me;
+
 	ack_APIC_irq();
-#ifdef CONFIG_X86_64
 	exit_idle();
-#endif
 	irq_enter();
 
 	me = smp_processor_id();