cpufreq_stats: Fix stats leak during update policy

When the cpufreq policy is moved from one CPU to another, the percpu
stats_table is overwritten and leaked. Properly free the old stats table
and ensure its protected in the non-sysfs paths of update policy and
acct_update_power. The sysfs entries are removed in the cpufreq core
driver before migrating the policy. We introduce a new spinlock
specifically for these operations to avoid needed to convert all the
other spinlocks into the irq safe variants since acct_update_power is
typically called in ISR context.

Change-Id: I95ff24c07834065cd0fd3c763a488a9843097a1d
Signed-off-by: Jason Hrycay <jason.hrycay@motorola.com>
Reviewed-on: https://gerrit.mot.com/921752


SLTApproved: Slta Waiver <sltawvr@motorola.com>
SME-Granted: SME Approvals Granted
Reviewed-by: Igor Kovalenko <igork@motorola.com>