md: make kobj_type structures constant

Since commit ee6d3dd ("driver core: make kobj_type constant.")
the driver core allows the usage of const struct kobj_type.

Take advantage of this to constify the structure definitions to prevent
modification at runtime.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230214-kobj_type-md-v1-1-d6853f707f11@weissschuh.net

Author: t-8ch

drivers/md/md.c

@@ -78,7 +78,7 @@
 static LIST_HEAD(pers_list);
 static DEFINE_SPINLOCK(pers_lock);
 
-static struct kobj_type md_ktype;
+static const struct kobj_type md_ktype;
 
 struct md_cluster_operations *md_cluster_ops;
 EXPORT_SYMBOL(md_cluster_ops);
@@ -3597,7 +3597,7 @@ static const struct sysfs_ops rdev_sysfs_ops = {
 	.show		= rdev_attr_show,
 	.store		= rdev_attr_store,
 };
-static struct kobj_type rdev_ktype = {
+static const struct kobj_type rdev_ktype = {
 	.release	= rdev_free,
 	.sysfs_ops	= &rdev_sysfs_ops,
 	.default_groups	= rdev_default_groups,
@@ -5555,7 +5555,7 @@ static const struct sysfs_ops md_sysfs_ops = {
 	.show	= md_attr_show,
 	.store	= md_attr_store,
 };
-static struct kobj_type md_ktype = {
+static const struct kobj_type md_ktype = {
 	.release	= md_kobj_release,
 	.sysfs_ops	= &md_sysfs_ops,
 	.default_groups	= md_attr_groups,