dt-bindings: arm: rockchip: Add Khadas Edge 2L board

dt-bindings: arm: rockchip: Add Khadas Edge 2L board

The Khadas Edge 2L is a single board computer based on the
Rockchip RK3576 SoC.

Specification:
- Rockchip RK3576
- 8/16GB LPDDR5
- 64/128GB eMMC 5.1
- AP6275P WiFi6 LAN
- HDMI2.1 Type-A
- MIPI-CSI x2
- MIPI-DSI x2
- USB3.1; USB2.0
- RTC clock
- PWM fan
- SPI Flash
- Pads expansion board (UART, USB)

Signed-off-by: Gray Huang <gray.huang@wesion.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://patch.msgid.link/20260317090731.600787-2-gray.huang@wesion.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>