CONFIG_MACH_D2NET_DT is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

LaCie d2 Network / Big Disk Network (Flattened Device Tree)

modulename: board-d2net.ko

configname: CONFIG_MACH_D2NET_DT

Linux Kernel Configuration
└─>Orion Implementations
└─>LaCie d2 Network / Big Disk Network (Flattened Device Tree)
In linux kernel since version 3.10 (release Date: 2013-06-30)  
Say 'Y' here if you want your kernel to support the
LaCie d2 Network NAS.

source code:
arch/arm/mach-orion5x/board-d2net.c