thermal/drivers/mediatek/lvts: Only update IRQ enable for valid sensors

thermal/drivers/mediatek/lvts: Only update IRQ enable for valid sensors

Only sensors that are valid need to have their interrupts enable status
updated based on their thresholds. Use the lvts_for_each_valid_sensor()
helper in lvts_update_irq_mask() to ignore invalid sensors.

Currently, since the invalid sensors will always contain zeroed out
thresholds (from kzalloc), they will always get their interrupts
disabled on this loop. So this commit doesn't change the resulting
interrupts configuration, but it slightly optimizes the loop by skipping
the invalid sensors, avoids potential future surprises if at some point
memory is no longer allocated for invalid sensors, as well as makes the
code more obvious.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Link: https://lore.kernel.org/r/20250113-mt8192-lvts-filtered-suspend-fix-v2-5-07a25200c7c6@collabora.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>