selftests: ocelot: tc_flower_chains: reorder interfaces

Use the standard interface order h1, swp1, swp2, h2 that is used by the
forwarding selftest framework. The previous order was confusing even
with the ASCII drawing. That isn't needed anymore.

This also drops the fixed MAC addresses and uses STABLE_MAC_ADDRS, which
ensures the MAC addresses are unique.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>