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

CONFIG_DAX_DRIVER (not configurable)

configname: CONFIG_DAX_DRIVER

Linux Kernel Configuration
└─>Device Drivers
└─>DAX_DRIVER
In linux kernel since version 3.10 (release Date: 2013-06-30)  
selects
CONFIG_DAX