As we have the pinctrl and clock support for the V3s SoC, it's now to
run a mainline Linux on it.

So add a .dtsi file for it.
Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
[Maxime: Removed the dependency on the CCU headers]
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>