fm10k: enable FTAG based forwarding

fm10k: enable FTAG based forwarding

This patch enables reading sglort (global resource tag) info into the
mbuf for RX and inserting an FTAG (Fabric Tag) at the beginning of the
packet for TX. The vlan_tci_outer field selected from rte_mbuf structure
for sglort is not used in fm10k now.
In FTAG based forwarding mode, the switch will forward packets according
to glort info in FTAG rather than mac and vlan table.

To activate this feature, user needs to pass a devargs parameter to eal
for fm10k device like "-w 0000:84:00.0,enable_ftag=1". Currently this
feature is supported only on PF, because FM10K_PFVTCTL register is
read-only for VF.

Signed-off-by: Wang Xiao W <xiao.w.wang@intel.com>
Acked-by: Jing Chen <jing.d.chen@intel.com>
Acked-by: John McNamara <john.mcnamara@intel.com>