thermal/drivers/mediatek: Change clk_prepare_enable to devm_clk_get_enabled in mtk_thermal_probe

Use devm_clk_get_enabled to do automatic resource management.
Meanwhile, remove error handling labels in the probe function and
the whole remove function.

Signed-off-by: Kang Chen <void0red@hust.edu.cn>
Reviewed-by: Dongliang Mu <dzm91@hust.edu.cn>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20230419020749.621257-2-void0red@hust.edu.cn