dt-bindings: serial: renesas,hscif: Document r8a779f0 bindings

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20220613131007.10027-1-wsa+renesas@sang-engineering.com


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