ANDROID: cpufreq: dt: invoke frequency-invariance setter function

Call the frequency-invariance setter function arch_set_freq_scale()
if the new frequency has been successfully set which is indicated by
dev_pm_opp_set_rate() returning 0.

Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Change-Id: I00dce40c8def07e87bce7bc556ffc3a8693af038
Signed-off-by: Chris Redpath <chris.redpath@arm.com>