arm: mvebu: Enable gpio-fan for Thecus N2350 board

Add gpio-fan in the DTS and enable the GPIO in board file to start the fan
during boot.

Note that this patch depends on
https://patchwork.ozlabs.org/project/uboot/patch/20230606214539.4229-1-mibodhi@gmail.com/



Signed-off-by: Tony Dinh <mibodhi@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>