CONFIG_CACHE_FLUSH_L1 is not available for thedefaultarchitecture x86.
Result is shown for architecture blackfin
default or selected kernelversion does not have config value CONFIG_CACHE_FLUSH_L1.
Result is shown for kernelversion 5.4.69

Locate cache flush funcs in L1 Inst Memory


Linux Kernel Configuration
└─>Blackfin Processor Options
└─>Blackfin Kernel Optimizations
└─>Locate cache flush funcs in L1 Inst Memory
In linux kernel since version 2.6.36 (release Date: 2010-10-20)  
If enabled, the Blackfin cache flushing functions are linked
into L1 instruction memory.

Note that this might be required to address anomalies, but
these functions are pretty small, so it shouldn't be too bad.
If you are using a processor affected by an anomaly, the build
system will double check for you and prevent it.