drm/i915: 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>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230216-kobj_type-i915-v1-1-ca65c9b93518@weissschuh.net

drivers/gpu/drm/i915/gt/intel_gt_sysfs.c

@@ -72,7 +72,7 @@ static void kobj_gt_release(struct kobject *kobj)
 {
 }
 
-static struct kobj_type kobj_gt_type = {
+static const struct kobj_type kobj_gt_type = {
 	.release = kobj_gt_release,
 	.sysfs_ops = &kobj_sysfs_ops,
 	.default_groups = id_groups,

drivers/gpu/drm/i915/gt/sysfs_engines.c

@@ -419,7 +419,7 @@ static void kobj_engine_release(struct kobject *kobj)
 	kfree(kobj);
 }
 
-static struct kobj_type kobj_engine_type = {
+static const struct kobj_type kobj_engine_type = {
 	.release = kobj_engine_release,
 	.sysfs_ops = &kobj_sysfs_ops
 };