CONFIG_MACH_OVERO is not available for the selected architecture x86.
Result is shown for architecture arm

Gumstix Overo board

modulename: board-overo.ko

configname: CONFIG_MACH_OVERO

Linux Kernel Configuration
└─>Gumstix Overo board
In linux kernel since version 2.6.28 (release Date: 2008-12-24)
source code:
selects
CONFIG_OMAP_PACKAGE_CBB


is selected by
CONFIG_SND_OMAP_SOC_OVERO