mlx4e: Do not attempt to offload VXLAN ports that are unrecognized

The mlx4e driver does not support more than one port for VXLAN offload.  As
such expecting the hardware to offload other ports is invalid since it
appears the parsing logic is used to perform Tx checksum and segmentation
offloads.  Use the vxlan_port number to determine in which cases we can
apply the offload and in which cases we can not.

Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>