wireguard-tools: fix category/description in menuconfig

wireguard-tools: fix category/description in menuconfig

wireguard-tools is trying to import the menuconfig section
from the wireguard package, but since it's not anymore in
the same makefile this seems to fail and wireguard-tools
ends up in "extra packages" category instead with other
odds and ends.

Same for the description, it's trying to import it from the
wireguard package but it fails so it only shows the line
written in this makefile.

remove the broken imports and add manually the entries
and description they were supposed to load

Fixes: ea980fb9c6de ("wireguard: bump to 20191226")
Signed-off-by: Alberto Bursi <bobafetthotmail@gmail.com>
[fix trailing whitespaces, add Fixes]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
(cherry picked from commit a4d52522c7fbc47a04215b8f04a2e1f7cf7aafea)