x86/idle: Remove is_idle flag

Upon removal of the idle_notifier, all accesses to the "is_idle" flag serve
no purpose.
Signed-off-by: Len Brown <len.brown@intel.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/e4a24197cf9c227fcd1ca2df09999eaec9052f49.1479449716.git.len.brown@intel.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/process.c

@@ -65,10 +65,6 @@ __visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = {
 };
 EXPORT_PER_CPU_SYMBOL(cpu_tss);
 
-#ifdef CONFIG_X86_64
-static DEFINE_PER_CPU(unsigned char, is_idle);
-#endif
-
 /*
  * this gets called so that we can store lazy state into memory and copy the
  * current task into the new thread.
@@ -241,13 +237,10 @@ static inline void play_dead(void)
 #ifdef CONFIG_X86_64
 void enter_idle(void)
 {
-	this_cpu_write(is_idle, 1);
 }
 
 static void __exit_idle(void)
 {
-	if (x86_test_and_clear_bit_percpu(0, is_idle) == 0)
-		return;
 }
 
 /* Called from interrupts to signify idle end */