thermal: exynos: remove parsing of samsung, tmu_noise_cancel_mode property

All SoCs use the same value (4) for the noise cancel mode so just
make it explicit and remove parsing of samsung,tmu_noise_cancel_mode
property.

There should be no functional changes caused by this patch.

Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>