bnx2x: DCB rework

create DCB related states in function state-machine
allow handling of DCB errors from FW
allow disablement of DCB in FW, when peer disappears or error
clean up unused functions/variables as pointed by
David Binderman <dcb314@hotmail.com>

Reported-by: David Binderman <dcb314@hotmail.com>
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>