CONFIG_MACH_LSXL_DT is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Buffalo Linkstation LS-XHL, LS-CHLv2 (Flattened Device Tree)

modulename: board-lsxl.ko

configname: CONFIG_MACH_LSXL_DT

Linux Kernel Configuration
└─>Marvell Kirkwood Implementations
└─>Buffalo Linkstation LS-XHL, LS-CHLv2 (Flattened Device Tree)
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Say 'Y' here if you want your kernel to support the
Buffalo Linkstation LS-XHL & LS-CHLv2 devices, using
Flattened Device Tree.

source code: