CONFIG_BIG_LITTLE is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

big.LITTLE support (Experimental)

configname: CONFIG_BIG_LITTLE

Linux Kernel Configuration
└─>Kernel Features
└─>big.LITTLE support (Experimental)
In linux kernel since version 3.13 (release Date: 2014-01-19)  
This option enables support selections for the big.LITTLE
system architecture.

selects
CONFIG_MCPM


is selected by
CONFIG_BL_SWITCHER