default or selected kernelversion does not have config value CONFIG_MTD_BFIN_ASYNC.
Result is shown for kernelversion 6.7-rc3

Blackfin BF533-STAMP Flash Chip Support

modulename: bfin-async-flash.ko

configname: CONFIG_MTD_BFIN_ASYNC

Linux Kernel Configuration
└─>Device Drivers
└─>Memory Technology Device (MTD) support
└─>Mapping drivers for chip access
└─>Blackfin BF533-STAMP Flash Chip Support
In linux kernel since version 2.6.27 (release Date: 2008-10-09)  
Map driver which allows for simultaneous utilization of
ethernet and CFI parallel flash.

If compiled as a module, it will be called bfin-async-flash.

source code: