dt-bindings: serial: sh-sci: Add support for r8a77965 (H)SCIF

Add documentation for r8a77965 compatible string to Renesas sci-serial
device tree bindings documentation.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>