MLK-11285-02 net:fec: add enet AVB Ubuntu Gstreamer demo support

MLK-11285-02 net:fec: add enet AVB Ubuntu Gstreamer demo support

Support Gstreamer AVB demo support.

ring1 -> ClassA, ring2 -> ClassB, ring0 -> Best Effort

For QoS: ring1 > ring2 > ring0
For bandwidth reverse:
      50% bandwidth -> ClassA
      33% bandwidth -> ClassB
      17% bandwidth -> Best effort queue

In general, ClassA run audio, ClassB run video.
Since AVB demo use big bandwidth streaming, video cost more than
33Mbps bandwidth, and with Qos limitation: ClassA >= ClassB > Best effort,
so we have to change ring2 bandwidth equal to ring1 bandwidth (50%).
After validate on FPGA, AVB demo can work fine for audio and video.

Signed-off-by: Fugang Duan <B38611@freescale.com>
(cherry picked from commit 93d6579a7b3d2dafa721c835df5d5f7d30ed386e)