bnx2x: dcb - send all unmapped priorities to same COS as L2

As a result of DCBX negotiation some priorities maybe untouched and still
unmapped to any COS; instead of sending them to COS0 we assign them
to the same COS as L2 traffic - to avoid collisions with storage class of
service.

Signed-off-by: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>