pc_pcan.py state config should be of type BusState

[torgrimb]

I just tested using the updated python-can binding with pyxcp. Works like magic, however I had to update the 'STATE' config to type BusState instead of string in pc_pcan.py in the transport to get mine to work at least.

[christoph2]

Ah OK, so far I've only tested SocketCAN communication.

[torgrimb]

I created a small oneliner fix with what worked for me at #52