arm64: dts: renesas: Refactor RZ/T2H EVK device tree

arm64: dts: renesas: Refactor RZ/T2H EVK device tree

The RZ/T2H EVK and RZ/N2H EVK are very similar boards.  As there is so
much overlap between these parts, common device tree entries are moved
to the new file rzt2h-n2h-evk-common.dtsi.

Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
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/20250617171957.162145-3-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>