[S390] cpu hotplug/idle: move cpu_die call to enabled context

There is no difference if cpu_die is called from enabled or disabled
context. Except that the fast_gup code might be called via
cpu_die -> idle_task_exit -> __mm_drop -> crst_table_free. Which in
turn grabs and releases a spinlock using the _bh ops, which is not
allowed in irq disabled context, since spin_unlock_bh will
unconditionally enable interrupts again.
To get rid of the warning emitted by the softirq code just move the
code to enabled context.

In this case this doesn't fix a bug, we just get rid of a warning.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/process.c

@@ -76,17 +76,17 @@ unsigned long thread_saved_pc(struct task_struct *tsk)
 static void default_idle(void)
 {
 	/* CPU is going idle. */
-	local_irq_disable();
-	if (need_resched()) {
-		local_irq_enable();
-		return;
-	}
 #ifdef CONFIG_HOTPLUG_CPU
 	if (cpu_is_offline(smp_processor_id())) {
 		preempt_enable_no_resched();
 		cpu_die();
 	}
 #endif
+	local_irq_disable();
+	if (need_resched()) {
+		local_irq_enable();
+		return;
+	}
 	local_mcck_disable();
 	if (test_thread_flag(TIF_MCCK_PENDING)) {
 		local_mcck_enable();