net/ixgbe: set VLAN strip flag for NEON Rx

net/ixgbe: set VLAN strip flag for NEON Rx

For NEON vector of IXGBE PMD, introduce new flag PKT_RX_VLAN_STRIPPED to
show the case that the VLAN is stripped from the VLAN tagged packet.

This is because that the old flag PKT_RX_VLAN_PKT only indicates that
the packet is VLAN tagged, but cannot show whether VLAN is in
m->vlan_tci or in the packet at present. So add new flag to show the
vlan has been stripped by the hardware and its tci is saved in
m->vlan_tci when vlan stripping is enabled in the RX configuration of
the IXGBE PMD.

Signed-off-by: Feifei Wang <feifei.wang2@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Acked-by: Haiyue Wang <haiyue.wang@intel.com>