board: rockchip: Add Edgeble Neu2 IO Board

Neural Compute Module 2(Neu2) IO board is an industrial form factor
IO board from Edgeble AI.

General features:
- microSD slot
- MIPI DSI connector
- 2x USB Host
- 1x USB OTG
- Ethernet
- mini PCIe
- Onboard PoE
- RS485, RS232, CAN
- Micro Phone array
- Speaker
- RTC battery slot
- 40-pin expansion

Neu2 needs to mount on top of this IO board in order to create complete
Edgeble Neural Compute Module 2(Neu2) IO platform.

Add support for it.

Signed-off-by: Jagan Teki <jagan@edgeble.ai>