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

Marvell's Brownstone Development Platform

modulename: brownstone.ko

configname: CONFIG_MACH_BROWNSTONE

Linux Kernel Configuration
└─>Marvell PXA168/910/MMP2 Implmentations
└─>Marvell's Brownstone Development Platform
In linux kernel since version 2.6.38 (release Date: 2011-03-14)  
Say 'Y' here if you want to support the Marvell MMP2-based
Brown Development Platform.
MMP2-based board can't be co-existed with PXA168-based &
PXA910-based development board. Since MMP2 is compatible to
ARMv7 architecture.

source code: