When cpufreq is disabled, the per-cpu variable would have been set to
NULL. Remove this unnecessary check.

[ Changelog from Saravana Kannan. ]
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Acked-by: NSaravana Kannan <skannan@codeaurora.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>