thermal: cpu_cooling: Merge cpufreq_apply_cooling() into cpufreq_set_cur_state()

cpufreq_apply_cooling() has a single caller, cpufreq_set_cur_state() and
cpufreq_set_cur_state() is an unnecessary wrapper over cpufreq_apply_cooling().

Get rid of it by merging both routines.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>