mlxsw: spectrum_trap: Add support for setting of packet trap group parameters

Implement support for setting of packet trap group parameters by
invoking the trap_group_init() callback with the new parameters.

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