CONFIG_MACH_NOKIA_N8X0 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Nokia N800/N810

modulename: board-n8x0.ko

configname: CONFIG_MACH_NOKIA_N8X0

Linux Kernel Configuration
└─>TI OMAP2/3/4 Specific Features
└─>Nokia N800/N810
In linux kernel since version 2.6.32 (release Date: 2009-12-02)  
source code:
arch/arm/mach-omap2/board-n8x0.c