cpufreq: mediatek: Use module_init and add module_exit

- Use module_init instead of device_initcall.
- Add a function for module_exit to unregister driver.
Signed-off-by: Jia-Wei Chang <jia-wei.chang@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/cpufreq/mediatek-cpufreq.c

@@ -580,7 +580,13 @@ static int __init mtk_cpufreq_driver_init(void)
 
 	return 0;
 }
-device_initcall(mtk_cpufreq_driver_init);
+module_init(mtk_cpufreq_driver_init)
+
+static void __exit mtk_cpufreq_driver_exit(void)
+{
+	platform_driver_unregister(&mtk_cpufreq_platdrv);
+}
+module_exit(mtk_cpufreq_driver_exit)
 
 MODULE_DESCRIPTION("MediaTek CPUFreq driver");
 MODULE_AUTHOR("Pi-Cheng Chen <pi-cheng.chen@linaro.org>");