CONFIG_SIBYTE_SB1250 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_SIBYTE_SB1250 (not configurable)

modulename: fixup-sb1250.ko

configname: CONFIG_SIBYTE_SB1250

Linux/MIPS Kernel Configuration
└─>Machine selection
└─>SIBYTE_SB1250
In linux kernel since version 2.6.12  
source code:
arch/mips/pci/