cpufreq: sparc: Don't allocate cpufreq_driver dynamically

There is no point allocating the cpufreq driver dynamically and add so
much complexity in the driver.

Do what is done for other cpufreq drivers and statically allocate the
cpufreq driver.

Reported-by: Markus Elfring <Markus.Elfring@web.de>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>