arm: actions: add S700 SoC device tree

This patch adds .dtsi file(sync with Linux 5.5-rc6 with hash "b3a987b0264d")
and required binding for S700 SoC that is a 64-bit Quad-core ARM
Cortex-A53 cores.

It also provisions dts file to be built based on selected
platform(CONFIG_MACH_S900/S700).

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Amit Singh Tomar <amittomer25@gmail.com>