CONFIG_CPU_BMIPS5000 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

BMIPS5000

configname: CONFIG_CPU_BMIPS5000

CPU type
└─>BMIPS5000
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  
Broadcom BMIPS5000 processors.