The ms5611 passes &indio_dev->dev as a parameter to all its IO callbacks
only to directly cast the struct device back to struct iio_dev. And the
struct iio_dev is then only used to get the drivers state struct.

Simplify this a bit by passing the state struct directly. This makes it a
bit easier to follow what the code is doing.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20211020142110.7060-1-lars@metafoo.deSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>