Fix compiler warnings generated when devfreq is not enabled
(CONFIG_PM_DEVFREQ is not set).
Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org> Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>