ARM: dts: rockchip: move shared tinker-board nodes to a common dtsi

Tinker Board and Tinker Board S share most of their components,
so should also not replicate these for each variant.

So move them to a shared dtsi that then can get included by both
boards.
Signed-off-by: David Summers <beagleboard@davidjohnsummers.uk>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>