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

CONFIG_CPU_HAS_WB (not configurable)

modulename: wbflush.ko

configname: CONFIG_CPU_HAS_WB

Linux Kernel Configuration
└─>Kernel type
└─>CPU_HAS_WB
In linux kernel since version 2.6.12  
source code:
is depended by
CONFIG_CPU_R3000