arm64: dts: rockchip: prepare NanoPC-T6 for LTS board

arm64: dts: rockchip: prepare NanoPC-T6 for LTS board

FriendlyELEC introduced a second version of NanoPC-T6 SBC.

Create common include file and make NanoPC-T6 use it. Following
patches will add LTS version.

Signed-off-by: Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>
Link: https://lore.kernel.org/r/20240829-friendlyelec-nanopc-t6-lts-v6-2-edff247e8c02@linaro.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
[ upstream commit: d14f3a4f1feabb6bb5935bf3b275a1e6bf2208eb ]

(cherry picked from commit e8b52bdfe5a1444edd1b9bb7cc10b9781d72cc84)
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Acked-by: Sumit Garg <sumit.garg@linaro.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>