xfrm: handle NETDEV_UNREGISTER for xfrm device

stable inclusion
from linux-4.19.114
commit cb2775c906eed8f350b8deed7d681bf285fbcb72

--------------------------------

commit 03891f82 upstream.

This patch to handle the asynchronous unregister
device event so the device IPsec offload resources
could be cleanly released.

Fixes: e4db5b61 ("xfrm: policy: remove pcpu policy cache")
Signed-off-by: NRaed Salem <raeds@mellanox.com>
Reviewed-by: NBoris Pismenny <borisp@mellanox.com>
Reviewed-by: NSaeed Mahameed <saeedm@mellanox.com>
Signed-off-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NLi Aichun <liaichun@huawei.com>
Reviewed-by: Nguodeqing <geffrey.guo@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

net/xfrm/xfrm_device.c

@@ -332,6 +332,7 @@ static int xfrm_dev_event(struct notifier_block *this, unsigned long event, void
 		return xfrm_dev_feat_change(dev);
 
 	case NETDEV_DOWN:
+	case NETDEV_UNREGISTER:
 		return xfrm_dev_down(dev);
 	}
 	return NOTIFY_DONE;