selftests: spectrum-2: Add delta two masks one key test

Ensure that the bug is fixed and we no longer have C-TCAM spill for two
keys that differ only in delta.

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>