netfilter: nf_tables_offload: Check for the NETDEV_UNREGISTER event

Check for the NETDEV_UNREGISTER event from the nft_offload_netdev_event
function, which is the event that actually triggers the clean up.

Fixes: 06d392cb ("netfilter: nf_tables_offload: remove rules when the device unregisters")
Signed-off-by: wenxu <wenxu@ucloud.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_offload.c

@@ -577,6 +577,9 @@ static int nft_offload_netdev_event(struct notifier_block *this,
 	struct net *net = dev_net(dev);
 	struct nft_chain *chain;
 
+	if (event != NETDEV_UNREGISTER)
+		return NOTIFY_DONE;
+
 	mutex_lock(&net->nft.commit_mutex);
 	chain = __nft_offload_get_chain(dev);
 	if (chain)