SAMV7 MCAN: use FIFO mode instead of QUEUE mode; improve error reporting

When using QUEUE mode sometimes the counting semaphore indicates there is no space left in the TX buffers, but in fact there is.  This leads to a situation, where all TX buffers are empty and the driver
still waits for space in the buffers.  The switch from QUEUE mode to FIFO mode is just a workarround to make the semaphore counting self repairing.

The Error reporting is changed due to some Error Interrupts not reporting states, they are reporting state changes. To keep this into Account the static Error conditions like WARNING, PASSIVE or BUS_OFF are filled in
every time.