docs: iio: fix bullet list formatting

This 2nd-level bullet list is not properly ReST-formatted and thus it gets
rendered as a unique paragraph quite unreadable.  Fix by adding spaces as
needed.

While there also swap "shift" and "repeat" so they are in the correct
order.

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Link: https://lore.kernel.org/r/20210215143511.25471-5-luca@lucaceresoli.net


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