iio: proximity: sx9324: Switch to DEFINE_SIMPLE_DEV_PM_OPS() and pm_sleep_ptr()

These new macros avoid the need for marking the callbacks __maybe_unused
whilst ensuring both callbacks and structure may be dropped by the compiler
if CONFIG_PM_SLEEP is not enabled.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Gwendal Grignou <gwendal@chromium.org>
Link: https://lore.kernel.org/r/20220807185618.1038812-3-jic23@kernel.org


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>