iio: dac: ad5380: align '*' each line and drop unneeded blank line

Tidy up a missing space before */ and a unwanted blank line between
function documentation  and code.

Signed-off-by: Jiang Jian <jiangjian@cdjrlc.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220621092319.69598-1-jiangjian@cdjrlc.com


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