doc: conf.py: correct title and author of generated pdf

Adjust the PDF output options for rst2pdf:

* Set start document to 'index'.
* Set title to 'Das U-Boot'.
* Set author to 'The U-Boot development community'.

Correct documentation link.

Remove obsolete FIXME.

Link: https://rst2pdf.org/static/manual.html
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
1 file changed