sfc: handle enc keys in efx_tc_flower_parse_match()

Translate the fields from flow dissector into struct efx_tc_match.
In efx_tc_flower_replace(), reject filters that match on them, because
 only 'foreign' filters (i.e. those for which the ingress dev is not
 the sfc netdev or any of its representors, e.g. a tunnel netdev) can
 use them.

Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>