net: microchip: sparx5: Add VCAP debugfs KUNIT test

This tests the functionality of the debugFS support:

- finding valid keyset on an address
- raw VCAP output
- full rule VCAP output

Signed-off-by: Steen Hegelund <steen.hegelund@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>