arm64: dts: rockchip: add px30-cobra base dtsi and board variants

Cobra are Touchscreen devices built around the PX30 SoC using
a variety of display options.

The devices feature an EMMC, network port, usb host + OTG ports and
a 720x1280 display with a touchscreen.

Signed-off-by: Heiko Stuebner <heiko.stuebner@cherry.de>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Link: https://lore.kernel.org/r/20250514150745.2437804-5-heiko@sntech.de


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