thermal: amlogic: Make amlogic_thermal_disable() return void

amlogic_thermal_disable() returned zero unconditionally and
amlogic_thermal_remove() already ignores the return value.

Make it return no value and modify amlogic_thermal_suspend to not check
the value.

This patch introduces no semantic changes, but makes it more obvious for
a human reader that amlogic_thermal_suspend() cannot fail.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20231116112633.668826-2-u.kleine-koenig@pengutronix.de