CONFIG_ARC_BOARD_ML509 is not available for thedefaultarchitecture x86.
Result is shown for architecture arc

ML509

configname: CONFIG_ARC_BOARD_ML509

Linux Kernel Configuration
└─>"Legacy" ARC FPGA dev Boards
└─>ML509
In linux kernel since version 3.1 (release Date: 2011-10-24)  
ARC ML509 FPGA Ref Platform (Xilinx Virtex-5 Based)