cpufreq: Break out early if freq equals to target_freq

Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
Signed-off-by:
franciscofranco <franciscofranco.1990@gmail.com>

idea is taken here -
https://github.com/franciscofranco/hammerhead/commit/63d46da4ea1b153a1d5e1b8cfeda71ad28af884c