mlxsw: spectrum: Use generic listener struct for events

Change the events to use the generic listener struct.
Merge the event list into the trap list, so the same functions will
handle both.

Signed-off-by: Nogah Frankel <nogahf@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>