thermal: exynos: Remove exynos_thermal_common.[c|h] files

After defining all necessary Exynos data in the device tree and heavy
reusage of the of-thermal.c those files can be removed.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>