examples/ip_pipeline: assign MAC address to routing ports

examples/ip_pipeline: assign MAC address to routing ports

As a result of tracking, output ports of routing pipelines are linked with
physical nic ports (potentially through other pipeline instances).
Thus, the mac addresses of the NIC ports are assigned to routing pipeline
out ports which are connected to them and are further used in routing table
entries instead of hardcoded default values.

Signed-off-by: Jasvinder Singh <jasvinder.singh@intel.com>
Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>