dt-bindings: ata: ahci-platform: Add rk3568-dwc-ahci compatible

Add SoC specific compatible for rk3568 ahci controller

Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220311210357.222830-6-linux@fw-web.de