nfp: remove false positive offloads in flower vxlan

Pass information to the match offload on whether or not the repr is the
ingress or egress dev. Only accept tunnel matches if repr is the egress
dev.

This means rules such as the following are successfully offloaded:
tc .. add dev vxlan0 .. enc_dst_port 4789 .. action redirect dev nfp_p0

While rules such as the following are rejected:
tc .. add dev nfp_p0 .. enc_dst_port 4789 .. action redirect dev vxlan0

Also reject non tunnel flows that are offloaded to an egress dev.
Non tunnel matches assume that the offload dev is the ingress port and
offload a match accordingly.

Fixes: 611aec10

 ("nfp: compile flower vxlan tunnel metadata match fields")
Signed-off-by: John Hurley <john.hurley@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>