net: dsa: remove "ds" and "port" from struct dsa_switchdev_event_work

By construction, the struct net_device *dev passed to
dsa_slave_switchdev_event_work() via struct dsa_switchdev_event_work
is always a DSA slave device.

Therefore, it is redundant to pass struct dsa_switch and int port
information in the deferred work structure. This can be retrieved at all
times from the provided struct net_device via dsa_slave_to_port().

For the same reason, we can drop the dsa_is_user_port() check in
dsa_fdb_offload_notify().

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>