CONFIG_MACH_D2NET is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

LaCie d2 Network

modulename: d2net-setup.ko

configname: CONFIG_MACH_D2NET

Linux Kernel Configuration
└─>Orion Implementations
└─>LaCie d2 Network
In linux kernel since version 2.6.32 (release Date: 2009-12-02)  
Say 'Y' here if you want your kernel to support the
LaCie d2 Network NAS.

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