Fix memory leak in cpufreq stats.

When system enters sleep, non-boot CPUs will be disabled.
Cpufreq stats sysfs is created when the CPU is up, but it is not
freed when the CPU is going down. This will cause memory leak.
Signed-off-by: Nxiaobing tu <xiaobing.tu@intel.com>
Signed-off-by: Nguifang tang <guifang.tang@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq_stats.c

@@ -328,6 +328,7 @@ static int __cpuinit cpufreq_stat_cpu_callback(struct notifier_block *nfb,
 		cpufreq_update_policy(cpu);
 		break;
 	case CPU_DOWN_PREPARE:
+	case CPU_DOWN_PREPARE_FROZEN:
 		cpufreq_stats_free_sysfs(cpu);
 		break;
 	case CPU_DEAD: