[SCSI] fcoe: use real dev in case of HW vlan acceleration

Use real dev in case it has HW vlan acceleration
support since in this case the real dev would
do needed vlan processing, this way unnecessary
vlan layer processing avoided and it gives
slightly better IOPS with 512B size IOs.

Signed-off-by: Vasu Dev <vasu.dev@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>