The driver should not flush the whole workqueue when only one work (the
pkey poll one) needs to be cancelled.  Use cancel_delayed_work_sync()
instead.
Signed-off-by: NErez Shitrit <erezsh@mellanox.com>
Signed-off-by: NOr Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: NRoland Dreier <roland@purestorage.com>