x86/apic: Remove local var in flat_send_IPI_allbutself()

No code changed:

  # arch/x86/kernel/apic/apic_flat_64.o:

   text    data     bss     dec     hex filename
   1838     624       0    2462     99e apic_flat_64.o.before
   1838     624       0    2462     99e apic_flat_64.o.after

md5:
   aa2ae687d94bc4534f86ae6865dabd6a  apic_flat_64.o.before.asm
   42148da76ba8f9a236c33f8803bd2a6b  apic_flat_64.o.after.asm

md5 sum is different due to asm output offsets changing.
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20171211115444.26577-1-bp@alien8.deSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/apic/apic_flat_64.c

@@ -84,12 +84,8 @@ flat_send_IPI_mask_allbutself(const struct cpumask *cpumask, int vector)
 static void flat_send_IPI_allbutself(int vector)
 {
 	int cpu = smp_processor_id();
-#ifdef	CONFIG_HOTPLUG_CPU
-	int hotplug = 1;
-#else
-	int hotplug = 0;
-#endif
-	if (hotplug || vector == NMI_VECTOR) {
+
+	if (IS_ENABLED(CONFIG_HOTPLUG_CPU) || vector == NMI_VECTOR) {
 		if (!cpumask_equal(cpu_online_mask, cpumask_of(cpu))) {
 			unsigned long mask = cpumask_bits(cpu_online_mask)[0];