net/mlx5: fix VXLAN VNI matching on ConnectX-5

net/mlx5: fix VXLAN VNI matching on ConnectX-5

In the recent update, the misc5 matcher was introduced to
match VxLAN header extra fields. However, ConnectX-5
doesn't support misc5 for the UDP ports different from
VXLAN's standard one (4789).

Need to fall back to the previous approach and use legacy
misc matcher if non-standard UDP port is recognized
in VxLAN flow.

Fixes: 630a587bfb37 ("net/mlx5: support matching on VXLAN reserved field")
Cc: stable@dpdk.org
Signed-off-by: Rongwei Liu <rongweil@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>