selftest: cpufreq: Add support to test cpufreq modules

This patch adds support for cpufreq modules like cpufreq drivers and
cpufreq governors. The tests will insert the modules in different orders
and them perform basic cpufreq tests. The modules are then removed from
the kernel.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>