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

PXA3xx Form Factor Platform (aka Littleton)

modulename: littleton.ko

configname: CONFIG_MACH_LITTLETON

Select target board
└─>PXA3xx Form Factor Platform (aka Littleton)
In linux kernel since version 2.6.25 (release Date: 2008-04-16)  
source code:
arch/arm/mach-pxa/littleton.c