erofs: make kobj_type structures constant

Since commit ee6d3dd4 ("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>
Acked-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20230209-kobj_type-erofs-v1-1-078c945e2c4b@weissschuh.netSigned-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

fs/erofs/sysfs.c

@@ -179,13 +179,13 @@ static const struct sysfs_ops erofs_attr_ops = {
 	.store	= erofs_attr_store,
 };
 
-static struct kobj_type erofs_sb_ktype = {
+static const struct kobj_type erofs_sb_ktype = {
 	.default_groups = erofs_groups,
 	.sysfs_ops	= &erofs_attr_ops,
 	.release	= erofs_sb_release,
 };
 
-static struct kobj_type erofs_ktype = {
+static const struct kobj_type erofs_ktype = {
 	.sysfs_ops	= &erofs_attr_ops,
 };
 
@@ -193,7 +193,7 @@ static struct kset erofs_root = {
 	.kobj	= {.ktype = &erofs_ktype},
 };
 
-static struct kobj_type erofs_feat_ktype = {
+static const struct kobj_type erofs_feat_ktype = {
 	.default_groups = erofs_feat_groups,
 	.sysfs_ops	= &erofs_attr_ops,
 };