iio: adc: ti-adc0832: Use devm managed functions for all of probe()

Simplifies error handling, plus allows us to drop the remove()
function entirely.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Reviewed-by: Alexandru Ardelean <aardelean@deviqon.com>
Link: https://lore.kernel.org/r/20210516172520.1398835-7-jic23@kernel.org