dt-bindings: ata: rcar-sata: Convert to json-schema

Convert the Renesas R-Car Serial-ATA Device Tree binding documentation
to json-schema.

While at it:
  - Remove the deprecated "renesas,rcar-sata" compatible value,
  - Add "iommus", "power-domains", and "resets" properties,
  - Update the example.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Rob Herring <robh@kernel.org>