repo: Add meta-seco-rockchip layer.

This layer adds oniro build configurations for Seco's reference
board Juno (SBC-D23), based on Rockchip processor PX30.

Thanks-to: Natalia Kovalenko <waykovalenko@gmail.com>

Relate-to: #4
Relate-to: https://booting.oniroproject.org/rzr/meta-oniro-blueprint-flutter/-/issues/4


Signed-off-by: Philippe Coval <philippe.coval.ext@huawei.com>