Update mcp_can.cpp
Update mcp_can.cpp

add 666kbps baudrate
wdross/CAN_BUS_Shield,adlerweb/CAN_BUS_Shield,Seeed-Studio/CAN_BUS_Shield,adlerweb/CAN_BUS_Shield,wdross/CAN_BUS_Shield,Seeed-Studio/CAN_BUS_Shield