dt-bindings: pinctrl: renesas: Document RZ/T2H and RZ/N2H SoCs

dt-bindings: pinctrl: renesas: Document RZ/T2H and RZ/N2H SoCs

Document the pin and GPIO controller IP for the Renesas RZ/T2H
(R9A09G077) and RZ/N2H (R9A09G087) SoCs, and add the shared DTSI header
file used by both the bindings and the driver.

The RZ/T2H SoC supports 729 pins, while RZ/N2H supports 576 pins.
Both share the same controller architecture; separate compatible strings
are added for each SoC to distinguish them.

Co-developed-by: Thierry Bultel <thierry.bultel.yh@bp.renesas.com>
Signed-off-by: Thierry Bultel <thierry.bultel.yh@bp.renesas.com>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: "Rob Herring (Arm)" <robh@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/20250808133017.2053637-2-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>