iio: addac: ad74413r: simplify with cleanup.h

Make use of mutex guard() and IIO iio_device_claim_direct_scoped() to
simplify code and error handling.

While at it, use devm_mutex_init() to initialize the mutex.

Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://patch.msgid.link/20241016-dev-ad74413r-minor-improv-v1-3-13c9c769237d@analog.com


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