ixgbe: priority tagging FCoE frames without FCoE offload

The DCB user priority for FCoE is available regardless of whether
FCoE offload is enabled (IXGBE_FLAG_FCOE_ENABLED bit is set).
This allows proper DCB user priority tagging for FCoE
traffic on both 82598 and 82599 devices.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>