cpufreq: Fix and clean up show_cpuinfo_cur_freq()

There is a missing newline in show_cpuinfo_cur_freq(), so add it,
but while at it clean that function up somewhat too.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: All applicable <stable@vger.kernel.org>