arm64: dts: exynos: Add initial support for Samsung Galaxy S20 5G (x1s)

arm64: dts: exynos: Add initial support for Samsung Galaxy S20 5G (x1s)

Add initial support for the Samsung Galaxy S20 5G (x1s/SM-G981B)
phone. It was launched in 2020, and it's based on the Exynos 990 SoC. It
has only one configuration with 12GB of RAM and 128GB of UFS 3.0 storage.

This device tree adds support for the following:

- SimpleFB
- 12GB RAM
- Buttons

Signed-off-by: Umer Uddin <umer.uddin@mentallysanemainliners.org>
Link: https://lore.kernel.org/r/20241209080059.11891-4-umer.uddin@mentallysanemainliners.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>