staging: iio: tsl2583: combine sysfs documentation

There are two separate files describing the tsl2583 sysfs attributes.
Combine the two files into one. Updated the name of the sysfs attributes
to match the current ABI.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Suggested-by: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>