cpufreq: stats: Fix memory leaks when updating stats table

The address for an element in the per-cpu cpufreq_stats_table variable
is overwritten in cpufreq_stats_update_policy_cpu(), but the memory
allocated at the address that gets overwritten is not freed beforehand.

Free the allocated memory beforehand to fix the memory leaks.

Signed-off-by: Sultanxda <sultanxda@gmail.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>