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

This reverts commit f05c7b7d.

That change was causing a regression in the generic-adc-thermal-probed
bootrr test as reported in the kernelci-results list [1].
A proper rework will take longer, so revert it for now.

[1] https://groups.io/g/kernelci-results/message/42660

Fixes: f05c7b7d

 ("thermal/drivers/mediatek: Use devm_of_iomap to avoid resource leak in mtk_thermal_probe")
Signed-off-by: Ricardo Cañuelo <ricardo.canuelo@collabora.com>
Suggested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20230525121811.3360268-1-ricardo.canuelo@collabora.com