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

CONFIG_CPU_USE_DOMAINS (not configurable)

configname: CONFIG_CPU_USE_DOMAINS

Linux Kernel Configuration
└─>CPU_USE_DOMAINS
In linux kernel since version 2.6.38 (release Date: 2011-03-14)  
This option enables or disables the use of domain switching
via the set_fs() function.

is selected by
CONFIG_SWP_EMULATE