bfd: schema: make link with bgp-router a complex type

Data associated with an IFMap link had to be made a complex type in order for
autogen scripts to work.

Change-Id: Ic60d8afb87c3b9ec395e4cb1fc6176be7c587ba6
Signed-off-by: Mateusz Zalega <mateusz.zalega@codilime.com>
Merge "bfd: schema: make link with bgp-router a complex type"