selftests: mlxsw: Add Bloom filter simple test

Add a test that exercises Bloom filter code.
Activate eRP table in the region by adding multiple rule patterns which
with very high probability use different entries in the Bloom filter.
Then send packets in order to check lookup hits on all relevant rules.

Signed-off-by: Nir Dotan <nird@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>