THe devfreq_update_stats() updates the 'struct devfreq_dev_status'
in order to get current status of devfreq device. It is only used
for the governors.

This patch moves the devfreq_update_stats() into devfreq directory.
Signed-off-by: NChanwoo Choi <cwchoi00@gmail.com>
Signed-off-by: NMyungJoo Ham <myungjoo.ham@samsung.com>