fs/proc: Fix memory leak in sysctl-restrict

In sysctl_restrict_open(), single_open() is used, so we should use the
corresponding single_release(), instead of seq_release(), otherwise it
will cause a memory leak.

Fixes: 6ac873e2f630 ("sysctl: restrict the writing for key parameters")
Signed-off-by: Juntong Deng <juntongdeng@tencent.com>
Signed-off-by: yilingjin <yilingjin@tencent.com>
Reviewed-by: Hui Li <caelli@tencent.com>
Signed-off-by: Jianping Liu <frankjpliu@tencent.com>

fs/proc/sysctl_write_forbid.c

@@ -129,7 +129,7 @@ static const struct file_operations sysctl_restrict_file_ops = {
 	.read    = seq_read,
 	.write	 = sysctl_restrict_write,
 	.llseek  = seq_lseek,
-	.release = seq_release
+	.release = single_release
 };
 
 static int __init sysctl_restrict_init(void)