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

Omicron DEVIXP

modulename: omixp-setup.ko

configname: CONFIG_MACH_DEVIXP

Linux Kernel Configuration
└─>Intel IXP4xx Implementation Options
└─>Omicron DEVIXP
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Say 'Y' here if you want your kernel to support the DEVIXP
board from OMICRON electronics GmbH.

source code: