soc: renesas: Add config option for RZ/V2N (R9A09G056) SoC

Add a new Kconfig option, ARCH_R9A09G056, to enable ARM64 platform support
for the Renesas RZ/V2N SoC. Default this option to "y" when ARCH_RENESAS is
enabled, ensuring that support for the RZ/V2N SoC is automatically included.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/20250407191628.323613-3-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>