staging: dpaa2-ethsw: destroy workqueue after deregistering the notifiers

We should destroy the switch workqueue only after deregistering the
switchdev notifiers. Without this fix, we could end up with switchdev
notifications on a draining workqueue and also with a lock up since the
netdevice reference count is increased (in port_switchdev_event) and not
decreased ever (since the workqueue did not run).
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Link: https://lore.kernel.org/r/20200721091919.20394-5-ioana.ciornei@nxp.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fsl-dpaa2/ethsw/ethsw.c

@@ -1628,8 +1628,6 @@ static int ethsw_remove(struct fsl_mc_device *sw_dev)
 
 	ethsw_teardown_irqs(sw_dev);
 
-	destroy_workqueue(ethsw->workqueue);
-
 	dpsw_disable(ethsw->mc_io, 0, ethsw->dpsw_handle);
 
 	for (i = 0; i < ethsw->sw_attr.num_ifs; i++) {
@@ -1640,6 +1638,9 @@ static int ethsw_remove(struct fsl_mc_device *sw_dev)
 	kfree(ethsw->ports);
 
 	ethsw_takedown(sw_dev);
+
+	destroy_workqueue(ethsw->workqueue);
+
 	fsl_mc_portal_free(ethsw->mc_io);
 
 	kfree(ethsw);