thermal: amlogic: Use DEFINE_SIMPLE_DEV_PM_OPS for PM functions

thermal: amlogic: Use DEFINE_SIMPLE_DEV_PM_OPS for PM functions

This macro has the advantage over SIMPLE_DEV_PM_OPS that we don't have to
care about when the functions are actually used, so the corresponding
__maybe_unused can be dropped.

Also make use of pm_ptr() to discard all PM related stuff if CONFIG_PM
isn't enabled.

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/20231116112633.668826-3-u.kleine-koenig@pengutronix.de