thermal: Exynos: Deletion of unnecessary checks before two function calls

The functions cpufreq_cooling_unregister() and thermal_zone_device_unregister()
test whether their argument is NULL and then return immediately.
Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>