devlink: Add packet trap group parameters support

Packet trap groups are used to aggregate logically related packet traps.
Currently, these groups allow user space to batch operations such as
setting the trap action of all member traps.

In order to prevent the CPU from being overwhelmed by too many trapped
packets, it is desirable to bind a packet trap policer to these groups.
For example, to limit all the packets that encountered an exception
during routing to 10Kpps.

Allow device drivers to bind default packet trap policers to packet trap
groups when the latter are registered with devlink.

The next patch will enable user space to change this default binding.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>