devicetree: add Onion Corporation vendor id

Please see https://onion.io/contact

 for details.

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12883/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>