default or selected kernelversion does not have config value CONFIG_MFD_STA2X11.
Result is shown for kernelversion 6.9.9

STMicroelectronics STA2X11

modulename: sta2x11-mfd.ko

configname: CONFIG_MFD_STA2X11

Linux Kernel Configuration
└─>Device Drivers
└─>Multifunction device drivers
└─>STMicroelectronics STA2X11
In linux kernel since version 3.1 (release Date: 2011-10-24)  
source code:
drivers/mfd//sta2x11-mfd.c


is selected by
CONFIG_GPIO_STA2X11

is depended by
CONFIG_STA2X11