iio: proximity: rfd77402: convert probe to device-managed functions

iio: proximity: rfd77402: convert probe to device-managed functions

This change converts the probe hook to register the IIO device with
devm_iio_device_register() and register a hook with
devm_add_action_or_reset() to put the device in powerdown when the driver
gets unloaded.

Since the PM suspend/resume functions need only a reference to the
i2c_client object (which can be obtained from the base device object), the
i2c_set_clientdata() call can be removed.

Signed-off-by: Alexandru Ardelean <aardelean@deviqon.com>
Link: https://lore.kernel.org/r/20210630131636.1563148-2-aardelean@deviqon.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>