iio: accel: adxl367: Use automated cleanup for locks and iio direct mode.

Switching to the iio_device_claim_direct_scoped() for state
and to guard() based unlocking of mutexes simplifies error handling
by allowing direct returns when an error is encountered.
Reviewed-by: Nuno Sa <nuno.a@analog.com>
Link: https://lore.kernel.org/r/20240128150537.44592-4-jic23@kernel.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>