thermal/drivers/mediatek/lvts_thermal: Handle IRQ on all controllers

There is a single IRQ handler for each LVTS thermal domain, and it is
supposed to check each of its underlying controllers for the origin of
the interrupt and clear its status. However due to a typo, only the
first controller was ever being handled, which resulted in the interrupt
never being cleared when it happened on the other controllers. Add the
missing index so interrupts are handled for all controllers.

Fixes: f5f633b1 ("thermal/drivers/mediatek: Add the Low Voltage Thermal Sensor driver")
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20230706153823.201943-2-nfraprado@collabora.com