netpoll: remove return value from netpoll_rx_disable()

The netpoll_rx_disable() will always return 0, it is no use and looks wordy,
so remove the unnecessary code and get rid of it in _dev_open and _dev_close.

Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index cec074b..37deedd 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -247,7 +247,7 @@
 	zap_completion_queue();
 }
 
-int netpoll_rx_disable(struct net_device *dev)
+void netpoll_rx_disable(struct net_device *dev)
 {
 	struct netpoll_info *ni;
 	int idx;
@@ -257,7 +257,6 @@
 	if (ni)
 		down(&ni->dev_lock);
 	srcu_read_unlock(&netpoll_srcu, idx);
-	return 0;
 }
 EXPORT_SYMBOL(netpoll_rx_disable);