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

BCM91250C2-LittleSur

configname: CONFIG_SIBYTE_LITTLESUR

BCM1xxx SOC-based board
└─>BCM91250C2-LittleSur
In linux kernel since version 2.6.12  

depends
 or CONFIG_EXPERIMENTAL