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.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>