Support GET_AVB_INFO command

[ahogen]

Andy Lucas removed GET_AVB_INFO response support back in 2013 (see here). No real comment from the author on this particular change. Commit comment only says

Enabled Talker on the DC endpoint and fixing Talker attributes

I wasn't under the impression that GET_AVB_INFO was Talker specific.

This change has propagated all the way into current 2017 code, over in the XMOS repos (see here). Since it reports very important status info, like asCapable, would it be worth re-integrating this command response?