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

CONFIG_SYS_HAS_CPU_BMIPS (not configurable)

configname: CONFIG_SYS_HAS_CPU_BMIPS

Linux Kernel Configuration
└─>CPU selection
└─>SYS_HAS_CPU_BMIPS
In linux kernel since version 3.14 (release Date: 2014-03-30)  
is selected by
CONFIG_CPU_BMIPS