network: link - simplify code a bit and remove some debug logging
man: fix example in systemd.link

'man/systemd.link.xml' recovery from:

commit eac684ef1c29684b1bcd27a89c38c202e568e469
Author: Tom Gundersen <teg@jklm.no>
Date:   Tue Feb 25 19:30:40 2014 +0100

    man: split out systemd.net{work,dev}(5) from systemd-networkd(8)
input_id: Recognize buttonless joystick types

Input devices like rudders or pedals are joystick-like; they don't have
buttons, but axes like RX, THROTTLE, or RUDDER. These don't interfere with
other device types with absolute axes (touch screens, touchpads, and
accelerometers), so it's fairly safe to mark them as ID_INPUT_JOYSTICK and thus
hand out dynamic ACLs to the user.

https://bugs.freedesktop.org/show_bug.cgi?id=70734