cpufreq: stats: Fix error handling in __cpufreq_stats_create_table()

Remove sysfs group if __cpufreq_stats_create_table() fails after creating
one.

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>