ixgbe: Distribute transmission of FCoE traffic in 82599

This adds a simple selection of a FCoE tx queue based on the current cpu id to
distribute transmission of FCoE traffic evenly among multiple FCoE transmit
queues.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>