CONFIG_SBC8641D is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

Wind River SBC8641D

modulename: sbc8641d.ko

configname: CONFIG_SBC8641D

86xx Board Type
└─>Wind River SBC8641D
In linux kernel since version 2.6.26 (release Date: 2008-07-13)  
This option enables support for the WRS SBC8641D board.

source code:
arch/powerpc/platforms/86xx/sbc8641d.c

depends
 or CONFIG_PPC_86xx