mm/damon/sysfs: make kobj_type structures constant

mm/damon/sysfs: 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.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Weißschuh <[email protected]>
Reviewed-by: SeongJae Park <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>