s390: simplify one-level sysctl registration for page_table_sysctl

There is no need to declare an extra tables to just create directory,
this can be easily be done with a prefix path with register_sysctl().

Simplify this registration.
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20230310234525.3986352-6-mcgrof@kernel.orgReviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/mm/pgalloc.c

@@ -33,19 +33,9 @@ static struct ctl_table page_table_sysctl[] = {
 	{ }
 };
 
-static struct ctl_table page_table_sysctl_dir[] = {
-	{
-		.procname	= "vm",
-		.maxlen		= 0,
-		.mode		= 0555,
-		.child		= page_table_sysctl,
-	},
-	{ }
-};
-
 static int __init page_table_register_sysctl(void)
 {
-	return register_sysctl_table(page_table_sysctl_dir) ? 0 : -ENOMEM;
+	return register_sysctl("vm", page_table_sysctl) ? 0 : -ENOMEM;
 }
 __initcall(page_table_register_sysctl);