cpufreq: s3c24xx: Fix broken s3c_cpufreq_init()

cpufreq: s3c24xx: Fix broken s3c_cpufreq_init()

commit a307a1e6bc0d "cpufreq: s3c: use cpufreq_generic_init()"
accidentally broke cpufreq on s3c2410 and s3c2412.

These two platforms don't have a CPU frequency table and used to skip
calling cpufreq_table_validate_and_show() for them.  But with the
above commit, we started calling it unconditionally and that will
eventually fail as the frequency table pointer is NULL.

Fix this by calling cpufreq_table_validate_and_show() conditionally
again.

Fixes: a307a1e6bc0d "cpufreq: s3c: use cpufreq_generic_init()"
Cc: 3.13+ <stable@vger.kernel.org> # v3.13+
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>