net: af_can: remove useless parameter 'err' in 'can_rx_register()'

Since commit bdfb5765 remove NULL-ptr checks from users of
can_dev_rcv_lists_find(). 'err' parameter is useless, so remove it.
Signed-off-by: Ye Bin <yebin10@huawei.com>
Link: https://lore.kernel.org/all/20221208090940.3695670-1-yebin@huaweicloud.comSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

net/can/af_can.c

@@ -446,7 +446,6 @@ int can_rx_register(struct net *net, struct net_device *dev, canid_t can_id,
 	struct hlist_head *rcv_list;
 	struct can_dev_rcv_lists *dev_rcv_lists;
 	struct can_rcv_lists_stats *rcv_lists_stats = net->can.rcv_lists_stats;
-	int err = 0;
 
 	/* insert new receiver  (dev,canid,mask) -> (func,data) */
 
@@ -481,7 +480,7 @@ int can_rx_register(struct net *net, struct net_device *dev, canid_t can_id,
 					       rcv_lists_stats->rcv_entries);
 	spin_unlock_bh(&net->can.rcvlists_lock);
 
-	return err;
+	return 0;
 }
 EXPORT_SYMBOL(can_rx_register);