x86/apic: Move ipi header into apic directory

Only used locally.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190722105219.434738036@linutronix.de

arch/x86/kernel/apic/bigsmp_32.c

@@ -4,18 +4,13 @@
  *
  * Drives the local APIC in "clustered mode".
  */
-#include <linux/threads.h>
 #include <linux/cpumask.h>
-#include <linux/kernel.h>
-#include <linux/init.h>
 #include <linux/dmi.h>
 #include <linux/smp.h>
 
-#include <asm/apicdef.h>
-#include <asm/fixmap.h>
-#include <asm/mpspec.h>
 #include <asm/apic.h>
-#include <asm/ipi.h>
+
+#include "ipi.h"
 
 static unsigned bigsmp_get_apic_id(unsigned long x)
 {