CONFIG_SIBYTE_BCM1125 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_SIBYTE_BCM1125 (not configurable)

configname: CONFIG_SIBYTE_BCM1125

Linux/MIPS Kernel Configuration
└─>Machine selection
└─>SIBYTE_BCM1125
In linux kernel since version 2.6.12