Documentation: devres: add missing IIO helpers

Documentation: devres: add missing IIO helpers

Add some missing device-managed helpers of iio to devres.rst.

devm_iio_kfifo_buffer_setup_ext() is introduced by commit 0a21526bc1d4 ("iio:
kfifo: add devm_iio_triggered_buffer_setup_ext variant").

devm_iio_triggered_buffer_setup_ext() is introduced by commit 5164c7889857 ("iio:
triggered-buffer: add {devm_}iio_triggered_buffer_setup_ext variants").

devm_iio_hw_consumer_alloc() is introduced by b688c18d3006 ("IIO: hw_consumer:
add devm_iio_hw_consumer_alloc").

devm_fwnode_iio_channel_get_by_name() is introduced by commit 1e64b9c5f9a0 ("iio:
inkern: move to fwnode properties").

Fixes: 0a21526bc1d4 ("iio: kfifo: add devm_iio_triggered_buffer_setup_ext variant")
Fixes: 5164c7889857 ("iio: triggered-buffer: add {devm_}iio_triggered_buffer_setup_ext variants")
Fixes: b688c18d3006 ("IIO: hw_consumer: add devm_iio_hw_consumer_alloc")
Fixes: 1e64b9c5f9a0 ("iio: inkern: move to fwnode properties")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20221103023402.1024437-1-yangyingliang@huawei.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>