thermal/drivers/mediatek/lvts_thermal: Register thermal zones as hwmon sensors

Register thermal zones as hwmon sensors to let userspace read
temperatures using standard hwmon interface.

Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20230613091317.1691247-1-wenst@chromium.org