iio: dac: ds4424: rename iio_info struct to avoid ambiguity

iio: dac: ds4424: rename iio_info struct to avoid ambiguity

Rename the static `ds4424_info` structure to `ds4424_iio_info`.

The previous name was generic and could be confused with chip-specific
data structures (like the upcoming `ds4424_chip_info`). The new name
explicitly indicates that this structure holds the IIO framework
callbacks.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>