mlxsw: Add NON_ROUTABLE trap

Add a trap for packets that the device decided to drop because they are
not supposed to be routed. For example, IGMP queries can be flooded by
the device in layer 2 and reach the router. Such packets should not be
routed and instead dropped.

Signed-off-by: Amit Cohen <amitc@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>