arm64: dts: exynos: add minimal support for exynosautov920 sadk board

ExynosAutov920 SADK is ExynosAutov920 SoC based SADK(Samsung Automotive
Development Kit) board. It has 16GB(8GB + 8GB) LPDDR5 RAM and 256GB
(128GB + 128GB) UFS.

This is minimal support board device-tree.
* Serial console
* GPIO Key
* PWM FAN

Signed-off-by: Jaewon Kim <jaewon02.kim@samsung.com>
Link: https://lore.kernel.org/r/20231208074527.50840-3-jaewon02.kim@samsung.com
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>