CONFIG_SIBYTE_BCM112X is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_SIBYTE_BCM112X (not configurable)

modulename: fixup-sb1250.ko

configname: CONFIG_SIBYTE_BCM112X

Linux Kernel Configuration
└─>SIBYTE_BCM112X
In linux kernel since version 2.6.12  
source code:
arch/mips/pci/