net/i40e: add outer VLAN processing

net/i40e: add outer VLAN processing

Outer VLAN processing is supported after firmware v8.4, kernel driver
also change the default behavior to support this feature. To align with
kernel driver, add support for outer VLAN processing in DPDK.

But it is forbidden for firmware to change the Inner/Outer VLAN
configuration while there are MAC/VLAN filters in the switch table.
Therefore, we need to clear the MAC table before setting config,
and then restore the MAC table after setting.

This will not impact on an old firmware.

Signed-off-by: Robin Zhang <robinx.zhang@intel.com>
Signed-off-by: Kevin Liu <kevinx.liu@intel.com>
Acked-by: Yuying Zhang <yuying.zhang@intel.com>