arm64: dts: rockchip: add NanoPC-T6 LTS

arm64: dts: rockchip: add NanoPC-T6 LTS

In the LTS (2310) version the miniPCIe slot got removed and USB 2.0
setup has changed. There are two external accessible ports and two ports
on the internal header.

There is an on-board USB hub which provides:
- one external connector (bottom one)
- two internal ports on pin header
- one port for m.2 E connector

The top USB 2.0 connector comes directly from the SoC.

Signed-off-by: Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>
Link: https://lore.kernel.org/r/20240829-friendlyelec-nanopc-t6-lts-v6-4-edff247e8c02@linaro.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>