cpufreq: powernv: Increase the verbosity of OCC console messages

Modify the OCC reset/load/active event message to make it clearer for
the user to understand the event and effect of the event.

Suggested-by: Stewart Smith <stewart@linux.vnet.ibm.com>
Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>