net: introduce netdev_alloc_pcpu_stats() for drivers

There are many drivers calling alloc_percpu() to allocate pcpu stats
and then initializing ->syncp. So just introduce a helper function for them.

Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 8433de4..25685e3 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -534,7 +534,6 @@
 {
 	struct macvlan_dev *vlan = netdev_priv(dev);
 	const struct net_device *lowerdev = vlan->lowerdev;
-	int i;
 
 	dev->state		= (dev->state & ~MACVLAN_STATE_MASK) |
 				  (lowerdev->state & MACVLAN_STATE_MASK);
@@ -546,16 +545,10 @@
 
 	macvlan_set_lockdep_class(dev);
 
-	vlan->pcpu_stats = alloc_percpu(struct vlan_pcpu_stats);
+	vlan->pcpu_stats = netdev_alloc_pcpu_stats(struct vlan_pcpu_stats);
 	if (!vlan->pcpu_stats)
 		return -ENOMEM;
 
-	for_each_possible_cpu(i) {
-		struct vlan_pcpu_stats *mvlstats;
-		mvlstats = per_cpu_ptr(vlan->pcpu_stats, i);
-		u64_stats_init(&mvlstats->syncp);
-	}
-
 	return 0;
 }