CONFIG_XILINX_ML300 is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

Xilinx-ML300

modulename: xilinx_ml300.ko

configname: CONFIG_XILINX_ML300

Machine Type
└─>Xilinx-ML300
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
This option enables support for the Xilinx ML300 evaluation board.