iio: dac: ad7303: convert probe to full device-managed

For this conversion, the regulators need to have some cleanup hooks
registered with devm_add_action_or_reset() and then the
devm_io_device_register() call can be used.

Signed-off-by: Alexandru Ardelean <aardelean@deviqon.com>
Link: https://lore.kernel.org/r/20210913115121.300082-1-aardelean@deviqon.com


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