arm64: dts: rockchip: Split rk3399-roc-pc for with and without mezzanine board.

For rk3399-roc-pc is a mezzanine board available that carries M.2 and
POE interfaces. Use it with a separate dts.

Signed-off-by: Markus Reichl <m.reichl@fivetechno.de>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/0fb4e21a-fe78-00aa-6142-ca8682a913eb@fivetechno.de


Signed-off-by: Heiko Stuebner <heiko@sntech.de>