staging: iio: tsl2583: fixed ordering of comments

in taos_defaults()

The comments in taos_defaults() appear after the line of code
that they apply to. This patch moves the comments so that they appear
before the code. Some of the comments were updated to be more
informative.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>