devlink: Add generic packet traps and groups

Add generic packet traps and groups that can report dropped packets as
well as exceptions such as TTL error.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>