thermal: exynos: remove parsing of samsung, tmu_default_temp_offset property

Trimming (one point based or two points based) is always used for
the temperature calibration and the default non-trimming code is
never reached. Remove it and then remove no longer needed parsing
of samsung,tmu_default_temp_offset 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>