handler.register_service: comment

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
topology: support OF1.2 and 1.4

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Reviewed-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
of_config: add OFPortStateType class

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>