arm64: dts: rockchip: Add dtsi file for RK3399S SoC variant

Following the hierarchical representation of the SoC data that's been already
established in the commit 296602b8 ("arm64: dts: rockchip: Move RK3399
OPPs to dtsi files for SoC variants"), add new SoC dtsi file for the Rockchip
RK3399S SoC, which is yet another variant of the Rockchip RK3399 SoC.

The only perceivable differences between the RK3399S and the RK3399 are in
the supported CPU DVFS OPPs, which result from the RK3399S being binned for
lower maximum CPU frequencies than the regular RK3399 variant.

The RK3399S variant is used in the Pine64 PinePhone Pro only, [1] whose board
dts file included the necessary adjustments to the CPU DVFS OPPs.  This commit
effectively moves those adjustments into the separate RK3399S SoC dtsi file,
following the above-mentioned "encapsulation" approach.

No functional changes are introduced, which was validated by decompiling and
comparing the affected dtb file before and after these changes.

[1] https://wiki.pine64.org/index.php/PinePhone_Pro



Signed-off-by: Dragan Simic <dsimic@manjaro.org>
Link: https://lore.kernel.org/r/c32622e4a6897378d9df81c8c3eda1bdb9211e0b.1728632052.git.dsimic@manjaro.org


Signed-off-by: Heiko Stuebner <heiko@sntech.de>