selftests: ocelot: add some example VCAP IS1, IS2 and ES0 tc offloads

Provide an example script which can be used as a skeleton for offloading
TCAM rules in the Ocelot switches.

Not all actions are demoed, mostly because of difficulty to automate
this from a single board.

For example, policing. We can set up an iperf3 UDP server and client and
measure throughput at destination. But at least with DSA setups, network
namespacing the individual ports is not possible because all switch
ports are handled by the same DSA master. And we cannot assume that the
target platform (an embedded board) has 2 other non-switch generator
ports, we need to work with the generator ports as switch ports (this is
the reason why mausezahn is used, and not IP traffic like ping). When
somebody has an idea how to test policing, that can be added to this
test.

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