cpufreq: tegra194: Remove the unneeded result variable

Return the value returned by smp_call_function_single() directly instead
of storing it in another redundant variable.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: ye xingchen <ye.xingchen@zte.com.cn>
[ Viresh: Minor update to commit log ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>