bnx2x: add a select queue callback

This callback required to allow FCoE traffic to be
sent on separate priority queue from other L2 traffic,
which is managed by PFC in HW.

Signed-off-by: Vladislav Zolotarov <vladz@broadcom.com>
Signed-off-by: Shmulik Ravid-Rabinovitz <shmulikr@broadcom.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>