iio: adc: Switch to sparse friendly iio_device_claim/release_direct()

iio: adc: Switch to sparse friendly iio_device_claim/release_direct()

Single patch for all the relatively simple cases.

These new functions allow sparse to find failures to release
direct mode reducing chances of bugs over the claim_direct_mode()
functions that are deprecated.

Cc: Olivier Moysan <olivier.moysan@foss.st.com>
Cc: Phil Reid <preid@electromag.com.au>
Reviewed-by: Mike Looijmans <mike.looijmans@topic.nl>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Link: https://patch.msgid.link/20250217141630.897334-30-jic23@kernel.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>