examples/ip_pipeline: link routing output ports to devices

examples/ip_pipeline: link routing output ports to devices

This commit implements tracking mechanism for linking routing pipeline
output ports to physical NIC ports.

Once all the pipelines of the application are initialised, mechanism is
invoked during post initialisation phase for relating routing pipeline
output with NIC ports by navigating through the intermediate pipelines,
if present.

The tracking functions of the pipelines which help in navigating through
the intermediate pipelines are moved from pipeline_<pipeline_name>_be.c
to pipeline_<pipeline_name>.c. All pipelines except passthrough pipelines
use default tracking function (pipeline/pipeline_common_fe.c).

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