net: vxlan: replace VXLAN_INVALID_HDR with VNI_NOT_FOUND

net: vxlan: replace VXLAN_INVALID_HDR with VNI_NOT_FOUND

Replace the drop reason "SKB_DROP_REASON_VXLAN_INVALID_HDR" with
"SKB_DROP_REASON_VXLAN_VNI_NOT_FOUND" in encap_bypass_if_local(), as the
latter is more accurate.

Fixes: 790961d88b0e ("net: vxlan: use kfree_skb_reason() in encap_bypass_if_local()")
Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>