staging: iio: ade7854: Use devm_iio_device_alloc
devm_iio_device_alloc makes code simpler.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Barry Song <21cnbao@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
authored by