bcache: make kobj_type structures constant

Since commit ee6d3dd4ed48 ("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 <[e-mail]>
Signed-off-by: Coly Li <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

drivers/md/bcache/bcache.h

···
 extern struct mutex bch_register_lock;
 extern struct list_head bch_cache_sets;
 
-extern struct kobj_type bch_cached_dev_ktype;
-extern struct kobj_type bch_flash_dev_ktype;
-extern struct kobj_type bch_cache_set_ktype;
-extern struct kobj_type bch_cache_set_internal_ktype;
-extern struct kobj_type bch_cache_ktype;
+extern const struct kobj_type bch_cached_dev_ktype;
+extern const struct kobj_type bch_flash_dev_ktype;
+extern const struct kobj_type bch_cache_set_ktype;
+extern const struct kobj_type bch_cache_set_internal_ktype;
+extern const struct kobj_type bch_cache_ktype;
 
 void bch_cached_dev_release(struct kobject *kobj);
 void bch_flash_dev_release(struct kobject *kobj);

drivers/md/bcache/sysfs.h

···
 #define _BCACHE_SYSFS_H_
 
 #define KTYPE(type)							\
-struct kobj_type type ## _ktype = {					\
+const struct kobj_type type ## _ktype = {					\
 	.release	= type ## _release,				\
 	.sysfs_ops	= &((const struct sysfs_ops) {			\
 		.show	= type ## _show,				\