default or selected kernelversion does not have config value CONFIG_MFD_SUPPORT.
Result is shown for kernelversion 6.2.5

Multifunction device drivers

configname: CONFIG_MFD_SUPPORT

Linux Kernel Configuration
└─>Device Drivers
└─>Multifunction device drivers
In linux kernel since version 2.6.35 (release Date: 2010-08-01)  
Multifunction devices embed several functions (e.g. GPIOs,
touchscreens, keyboards, current regulators, power management chips,
etc...) in one single integrated circuit. They usually talk to the
main CPU through one or more IRQ lines and low speed data busses (SPI,
I2C, etc..). They appear as one single device to the main system
through the data bus and the MFD framework allows for sub devices
(a.k.a. functions) to appear as discrete platform devices.
MFDs are typically found on embedded platforms.

This option alone does not add any kernel code.