Revert "net: dsa: mv88e6xxx: flush switchdev FDB workqueue before removing VLAN"

This reverts commit 2566a89b9e which is
commit a2614140dc upstream.

The above change depends on upstream commit 0faf890fc5 ("net: dsa:
drop rtnl_lock from dsa_slave_switchdev_event_work"), which is not
present in linux-5.15.y. Without that change, waiting for the switchdev
workqueue causes deadlocks on the rtnl_mutex.

Backporting the dependency commit isn't trivial/desirable, since it
requires that the following dependencies of the dependency are also
backported:

df405910ab net: dsa: sja1105: wait for dynamic config command completion on writes too
eb016afd83 net: dsa: sja1105: serialize access to the dynamic config interface
2468346c56 net: mscc: ocelot: serialize access to the MAC table
f7eb4a1c08 net: dsa: b53: serialize access to the ARL table
cf231b436f net: dsa: lantiq_gswip: serialize access to the PCE registers
338a3a4745 net: dsa: introduce locking for the address lists on CPU and DSA ports

and then this bugfix on top:

8940e6b669 ("net: dsa: avoid call to __dev_set_promiscuity() while rtnl_mutex isn't held")

Reported-by: Daniel Suchy <danny@danysek.cz>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/dsa/dsa.c

@@ -349,7 +349,6 @@ void dsa_flush_workqueue(void)
 {
 	flush_workqueue(dsa_owq);
 }
-EXPORT_SYMBOL_GPL(dsa_flush_workqueue);
 
 int dsa_devlink_param_get(struct devlink *dl, u32 id,
 			  struct devlink_param_gset_ctx *ctx)

net/dsa/dsa_priv.h

@@ -170,6 +170,7 @@ void dsa_tag_driver_put(const struct dsa_device_ops *ops);
 const struct dsa_device_ops *dsa_find_tagger_by_name(const char *buf);
 
 bool dsa_schedule_work(struct work_struct *work);
+void dsa_flush_workqueue(void);
 const char *dsa_tag_protocol_to_str(const struct dsa_device_ops *ops);
 
 static inline int dsa_tag_protocol_overhead(const struct dsa_device_ops *ops)