dt-bindings: net: renesas-gbeth: Add support for RZ/V2N (R9A09G056) SoC

Document support for the GBETH IP found on the Renesas RZ/V2N (R9A09G056)
SoC. The GBETH controller on the RZ/V2N SoC is functionally identical to
the one found on the RZ/V2H(P) (R9A09G057) SoC, so `renesas,rzv2h-gbeth`
will be used as a fallback compatible.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20250507173551.100280-1-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>