cpufreq: qoriq: Remove __exit macro from .exit callback

.exit callback (qoriq_cpufreq_cpu_exit()) is also used during suspend.
So __exit macro should be removed or the function will be discarded.

Signed-off-by: Jia Hongtao <hongtao.jia@nxp.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>