cpufreq: mediatek: Use module_init and add module_exit

stable inclusion
from stable-v5.10.121
commit 9d91400fff46b221806befc843654e5f5f38a82b
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5L6CQ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9d91400fff46b221806befc843654e5f5f38a82b

--------------------------------

[ Upstream commit b7070187 ]

- Use module_init instead of device_initcall.
- Add a function for module_exit to unregister driver.
Signed-off-by: NJia-Wei Chang <jia-wei.chang@mediatek.com>
Reviewed-by: NAngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

drivers/cpufreq/mediatek-cpufreq.c

@@ -579,7 +579,13 @@ 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>");