dt-bindings: gpio: rcar: Add r8a7744 (RZ/G1N) support

Renesas RZ/G1N (R8A7744) SoC GPIO blocks are identical to the R-Car Gen2
family. Add support for its GPIO controllers.

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>