be2net: allow offloading with the same port for IPv4 and IPv6

The callback for adding vxlan port can be called with the same port for both
IPv4 and IPv6. Do not disable the offloading if this occurs.

Signed-off-by: Jiri Benc <jbenc@redhat.com>
Acked-by: Sathya Perla <sathya.perla@avagotech.com>
Signed-off-by: David S. Miller <davem@davemloft.net>