selftests: forwarding: Introduce tc flower matching tests

Add first part of flower tests. This patch only contains dst/src ip/mac
matching.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>