CONFIG_X86_GENERICARCH is not available for thedefaultarchitecture x86.
Result is shown for architecture i386
default or selected kernelversion does not have config value CONFIG_X86_GENERICARCH.
Result is shown for kernelversion 5.4.123

Generic architecture (Summit, bigsmp, ES7000, default)

modulename: es7000plat.ko

configname: CONFIG_X86_GENERICARCH

Subarchitecture Type
└─>Generic architecture (Summit, bigsmp, ES7000, default)
In linux kernel since version 2.6.12  
This option compiles in the Summit, bigsmp, ES7000, default subarchitectures.
It is intended for a generic binary kernel.

source code:
depends
CONFIG_SMP