net/e1000: report VLAN extend capability

net/e1000: report VLAN extend capability

The rte_eth_dev_set_vlan_offload function will check vlan rx offload
capability, the i350/i210/i211 nics have vlan extend feature but
DEV_RX_OFFLOAD_VLAN_EXTEND is not set into the capability, that will
cause setting fail. So need to add this capability in
igb_get_rx_port_offloads_capa function.

Fixes: ef990fb56e55 ("net/e1000: convert to new Rx offloads API")
Cc: stable@dpdk.org
Signed-off-by: Zhihong Peng <zhihongx.peng@intel.com>
Reviewed-by: Wei Zhao <wei.zhao1@intel.com>