RX traffic counter test
Add feature test for RX traffic counter.
This one should cover stuff like:
- RX counter is incremented when frame is received at EOF. (No need to verify exact position within EOF, this should be done in ISO conformance tests)
- RX counter is not incremented when received frame is corrupted by error frame.
- RX counter is not incremented when frame is transmitted.
- RX counter is not cleared by COMMAND[TXFRCRST].
- RX counter is cleared by COMMAND[RXFRCRST].