parisc: pdc_stable: Constify struct kobj_type

This 'struct kobj_type' is not modified. It is only used in
kobject_init_and_add() which takes a 'const struct kobj_type *ktype'
parameter.

Constifying this structure and moving it to a read-only section,
and can increase over all security.

Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
Signed-off-by: Helge Deller <deller@gmx.de>