CONFIG_META21_FPGA is not available for thedefaultarchitecture x86.
Result is shown for architecture metag
default or selected kernelversion does not have config value CONFIG_META21_FPGA.
Result is shown for kernelversion 6.7-rc3

Meta 2.1 FPGA

configname: CONFIG_META21_FPGA

SoC Type
└─>Meta 2.1 FPGA
In linux kernel since version 3.1 (release Date: 2011-10-24)  
This is a Meta 2.1 FPGA bitstream, just a bare CPU.