mlxsw: spectrum: Free resources upon vPort destruction

There are situations in which a vPort is destroyed while still holding
references to device's resources such as FIDs and FDB records. This can
happen, for example, when a VLAN device is deleted while still being
bridged.

Instead of trying to make sure vPort destruction is invoked when it no
longer uses device's resources, just free them upon destruction. This
simplifies the code, as we no longer need to take different situations
into account when events are received - cleanup is taken care of in one
place.

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