board: rockchip: add Xunlong Orange Pi 5 Max

board: rockchip: add Xunlong Orange Pi 5 Max

The 5 Max is another board in the Orange Pi 5 family.

It's overall similar to the 5 Plus, but in a smaller form factor,
which leads to some I/O being reshuffled, but nothing relevant
to u-boot.

So, just reuse the config for the 5 Plus and adjust the DT names.

Reviewed-by: Jonas Karlman <jonas@kwiboo.se>
Signed-off-by: Ilya Katsnelson <me@0upti.me>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>