[Virtio-msg] Virtio message loopback

Hello,

As discussed yesterday during the call, I have prepared the list of instructions to reproduce my virtio-msg loopback setup. Please give a try and lemme know if something doesn't work.

This is based on the latest version of the spec (from Bill's latest pull request today).

-- Viresh

[1] https://linaro.atlassian.net/wiki/spaces/HVAC/pages/30104092673