cpufreq: Do not default-yes CPU_FREQ_STAT

CPU frequency transition statistics are not absolutely required for
proper cpufreq operation on the system AFAICT so remove the default-yes
setting in Kconfig.

Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>