CONFIG_CPU_FREQ is not available for thedefaultarchitecture x86.
Result is shown for architecture blackfin

CONFIG_CPU_FREQ (not configurable)

modulename: cpu-pxa.ko

and/or

cpu-omap.ko

and/or

cpu.ko

and/or

cpufreq.ko

configname: CONFIG_CPU_FREQ

Blackfin Kernel Configuration
└─>CPU Frequency scaling
└─>CPU_FREQ
In linux kernel since version 2.6.24 (release Date: 2008-01-24)  
If you want to enable this option, you should select the
DPMC driver from Character Devices.

source code: