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

Marvell GuruPlug Reference Board (Flattened Device Tree)

modulename: board-guruplug.ko

configname: CONFIG_MACH_GURUPLUG_DT

Linux Kernel Configuration
└─>Marvell Kirkwood Implementations
└─>Marvell GuruPlug Reference Board (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
Marvell GuruPlug Reference Board (Flattened Device Tree).

source code:
arch/arm/mach-kirkwood/board-guruplug.c