arm64: dts: rockchip: hook up the MCU on the QNAP TS433

The MCU is an important part of the device functionality. It provides
functionality like fan-control, more leds, etc and even more important
without it, the NAS-device cannot even fully turned off.

Hook up the serial device to its uart and hook into the thermal
management to control the fan according to the cpu temperature.

While the MCU also provides a temperature sensor for the case, this one
is just polled and does not provide functionality for handling trip
points in hardware, so a lot of polling would be involved.
As the cpu is only cooled passively in these devices, it's temperature
rising will indicate the temperature level of the system just earlier.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20241107114712.538976-9-heiko@sntech.de