iio: adc: stm32-dfsdm: Switch to sparse friendly iio_device_claim/release_direct()

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.

Reviewed-by: Olivier Moysan <olivier.moysan@foss.st.com>
Link: https://patch.msgid.link/20250217141630.897334-9-jic23@kernel.org


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