staging: r8188eu: Provide a TODO file for this driver

Provide a TODO file that lists the tasks that should be carried out in
order to move this driver off drivers/staging.

Acked-by: Phillip Potter <phil@philpotter.co.uk>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Link: https://lore.kernel.org/r/20210827100813.18610-1-fmdefrancesco@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>