default or selected kernelversion does not have config value CONFIG_KHADAS_MCU_FAN_THERMAL.
Result is shown for kernelversion 6.9-rc1

Khadas MCU controller FAN cooling support

modulename: khadas_mcu_fan.ko

configname: CONFIG_KHADAS_MCU_FAN_THERMAL

Linux Kernel Configuration
└─>Device Drivers
└─>Thermal drivers
└─>Device Tree and Open Firmware support
└─>Khadas MCU controller FAN cooling support
In linux kernel since version 5.1 (release Date: 2019-05-05)  
If you say yes here you get support for the FAN controlled
by the Microcontroller found on the Khadas VIM boards.

source code: