cpuidle / ACPI: fix potential NULL pointer dereference

The dereference should be moved below the NULL test.

dpatch engine is used to auto generate this patch.
(https://github.com/weiyj/dpatch)
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NLen Brown <len.brown@intel.com>

drivers/acpi/processor_idle.c

@@ -1132,7 +1132,7 @@ static int acpi_processor_setup_cpuidle_states(struct acpi_processor *pr)
 int acpi_processor_hotplug(struct acpi_processor *pr)
 {
 	int ret = 0;
-	struct cpuidle_device *dev = per_cpu(acpi_cpuidle_device, pr->id);
+	struct cpuidle_device *dev;
 
 	if (disabled_by_idle_boot_param())
 		return 0;
@@ -1147,6 +1147,7 @@ int acpi_processor_hotplug(struct acpi_processor *pr)
 	if (!pr->flags.power_setup_done)
 		return -ENODEV;
 
+	dev = per_cpu(acpi_cpuidle_device, pr->id);
 	cpuidle_pause_and_lock();
 	cpuidle_disable_device(dev);
 	acpi_processor_get_power_info(pr);