CONFIG_XILINX_VIRTEX440_GENERIC_BOARD is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

Generic Xilinx Virtex 5 FXT board support


Linux Kernel Configuration
└─>Generic Xilinx Virtex 5 FXT board support
In linux kernel since version 2.6.27 (release Date: 2008-10-09)  
This option enables generic support for Xilinx Virtex based boards
that use a 440 based processor in the Virtex 5 FXT FPGA architecture.

The generic virtex board support matches any device tree which
specifies 'xlnx,virtex440' in its compatible field. This includes
the Xilinx ML5xx reference designs using the powerpc core.

Most Virtex 5 designs should use this unless it needs to do some
special configuration at board probe time.