thermal/drivers/mediatek: Use devm_of_iomap to avoid resource leak in mtk_thermal_probe

Smatch reports:
1. mtk_thermal_probe() warn: 'apmixed_base' from of_iomap() not released.
2. mtk_thermal_probe() warn: 'auxadc_base' from of_iomap() not released.

The original code forgets to release iomap resource when handling errors,
fix it by switch to devm_of_iomap.

Fixes: 89945047

 ("thermal: mediatek: Add tsensor support for V2 thermal system")
Signed-off-by: Kang Chen <void0red@hust.edu.cn>
Reviewed-by: Dongliang Mu <dzm91@hust.edu.cn>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20230419020749.621257-1-void0red@hust.edu.cn