oy path
    at that point ttm should be the only piece of code interacting
    with the object so atomic_set is safe here.
v3: callback move notify only once the bo is in its new position
    call move notify want swaping out the buffer
v4:- don't call move_notify when swapin out bo, assume driver should
     do what is appropriate in swap notify
   - move move_notify call back to ttm_bo_cleanup_memtype_use for
     destroy path

Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
>ƒŽ‡š.x