arm64: dts: renesas: r9a09g077m44-rzt2h-evk: Add user LEDs

arm64: dts: renesas: r9a09g077m44-rzt2h-evk: Add user LEDs

Add USER LED0-LED8, which are available on RZ/T2H EVK.

In addition, move the header file inclusion into the common
rzt2h-n2h-evk-common.dtsi, so that both RZ/T2H and RZ/N2H EVK DTS/I
files share the same set of bindings.  This avoids duplication and keeps
the board files consistent.

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/20250820200659.2048755-3-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>