sfc: offload left-hand side rules for conntrack

Handle the (comparatively) simple case of a -trk rule on an efx netdev
 (i.e. not a tunnel decap rule) with ct and goto chain actions.

Reviewed-by: Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@amd.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>