arm64: dts: exynos: add initial devicetree support for exynos7870

Exynos7870 is an arm64 SoC manufactured by Samsung and announced in
2016. It is present in multiple mid-range Samsung phones and tablets.

Add basic devicetree support for the SoC, which includes CMUs, pin
controllers, I2C, UART, DW-MMC, and USB-DRD.

Signed-off-by: Kaustabh Chakraborty <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Krzysztof Kozlowski <[email protected]>

Author: Kaustabh Chakraborty