oonf-olsrd2: update to current develop branch - fixes routing#899

oonf-olsrd2: update to current develop branch - fixes routing#899

Development of OONF is very slow. The master branch is completely out of
date and new releases haven't been tagged since 2018.
According to this PR https://github.com/OLSR/OONF/pull/49#issuecomment-1229195523 the authors will probably just abandon the current master branch and replace it by the develop branch.
During my testing, the current development branch is more stable than
the latest tagged version on current OpenWrt versions.

Signed-off-by: Jakob Riepler <jakob+openwrt@chaosfield.at>