drivers: can: add bit error counter

The bit error counter is incremented when the CAN controller is unable to
transmit either a dominant or a recessive bit.

This new error counter should only be incremented directly if the CAN
controller is unable to distinquish between failure to transmit a dominant
versus failure to transmit a recessive bit. If the CAN controller supports
distinguishing between the two, either the `bit0` or `bit1` error counter
shall be incremented instead. Incrementing one of these will automatically
increment the bit error count as well.

Typically, a CAN controller driver will either use this new bit error
counter or the discrete bit0 and bit1 error counters depending on the
features supported by the hardware. Mixing the two on driver level should
not be required.

Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>