CONFIG_CPU_HAS_SR_RB is not available for thedefaultarchitecture x86.
Result is shown for architecture sh

CONFIG_CPU_HAS_SR_RB (not configurable)

configname: CONFIG_CPU_HAS_SR_RB

Linux Kernel Configuration
└─>Processor features
└─>CPU_HAS_SR_RB
In linux kernel since version 2.6.16 (release Date: 2006-03-19)  
This will enable the use of SR.RB register bank usage. Processors
that are lacking this bit must have another method in place for
accomplishing what is taken care of by the banked registers.

See Documentation/sh/register-banks.txt for further
information on SR.RB and register banking in the kernel in general.