CONFIG_MIPS_SEAD is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

MIPS SEAD board (EXPERIMENTAL)

configname: CONFIG_MIPS_SEAD

System type
└─>MIPS SEAD board (EXPERIMENTAL)
In linux kernel since version 2.6.12  
This enables support for the MIPS Technologies SEAD evaluation
board.