dt-bindings: power: renesas,rcar-sysc: Document r8a779g0 SYSC bindings

Document bindings for the R-Car V4H (aka R8A779G0) SYSC block.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220420084255.375700-5-yoshihiro.shimoda.uh@renesas.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>