since simtrace supports multiple application, but currently not
at the same time, the feature support is not app specific
Change-Id: I98ff92450cc2a247b294d2e15df171f3fe7c5156
We now generalize the USB communiction and abandon the 'req_ctx'
structure inherited from openpcd. Instead we use the libosmocore 'msgb'
structure to handle incoming and outgoing USB tranfers. We also use
linuxlist-based msgb-queues for each endpoint.