VT: ECN implementation.

[Problem] ecn value needs to be updated but there is no interface
  to update the ecn value.
[Solution]
  1. Implement interface to set ecn value into socket by
     setsockopt(). ecn value will be taking care by upper layer.
  2. Configured rx socket to get TOS header then from that extract
      ECN bits and based on CE bit handle the bitrate using TMMBR.

Bug: 216214250
Test: manual

Change-Id: I332803190c3e170fee183d15dfe2d49c36007aff
Signed-off-by: Jainishkumar Anghan <jai.anghan@samsung.com>