dt-bindings: serial: snps-dw-apb-uart: Document Rockchip RV1126

Document compatible string for Rockchip RV1126 SoC.

Signed-off-by: Jagan Teki <jagan@edgeble.ai>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220723204335.750095-13-jagan@edgeble.ai


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>