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

Generic Xilinx Virtex board

modulename: virtex.ko


Linux Kernel Configuration
└─>Generic Xilinx Virtex board
In linux kernel since version 2.6.24 (release Date: 2008-01-24)  
This option enables generic support for Xilinx Virtex based boards.

The generic virtex board support matches any device tree which
specifies 'xilinx,virtex' in its compatible field. This includes
the Xilinx ML3xx and ML4xx reference designs using the powerpc

Most Virtex designs should use this unless it needs to do some
special configuration at board probe time.

source code: