iio: light: cm32181: Add PM support

The read on in_illuminance_input keeps at 0 after system sleep.

So add proper suspend and resume callback to make the sensor keep
working after system sleep.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Link: https://lore.kernel.org/r/20220707000151.33381-1-kai.heng.feng@canonical.com


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