CONFIG_MIPS_SEAD3 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips
default or selected kernelversion does not have config value CONFIG_MIPS_SEAD3.
Result is shown for kernelversion 6.5.1

MIPS SEAD3 board

configname: CONFIG_MIPS_SEAD3

System type
└─>MIPS SEAD3 board
In linux kernel since version 3.1 (release Date: 2011-10-24)  
This enables support for the MIPS Technologies SEAD3 evaluation
board.