thermal: cpu_cooling: Replace kmalloc with kmalloc_array

Checkpatch reports following:

WARNING: Prefer kmalloc_array over kmalloc with multiply
+	cpufreq_cdev->freq_table = kmalloc(sizeof(*cpufreq_cdev->freq_table) * i,

Fix that.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>