cpufreq: powernv: Add sysfs attributes to show throttle stats

cpufreq: powernv: Add sysfs attributes to show throttle stats

BugLink: http://bugs.launchpad.net/bugs/1555765
Create sysfs attributes to export throttle information in
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory. The
newly added sysfs files are as follows:

 1)/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/turbo_stat
 2)/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/sub-turbo_stat
 3)/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/unthrottle
 4)/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/powercap
 5)/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overtemp
 6)/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/supply_fault
 7)/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overcurrent
 8)/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/occ_reset

Detailed explanation of each attribute is added to
Documentation/ABI/testing/sysfs-devices-system-cpu

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>
(cherry picked from commit 1b0289848d5dcea74a6e5115d6c9892b0dbe9c8f)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>