Use USART 0 connected to the SIM card side to sniff the communication.
The card side can also measure ETU times.
Do proper pin initialization.
This code can already capture the ATR communication between phone and card.
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.