xfrm: Do not allocate stats in the driver

With commit 34d21de9 ("net: Move {l,t,d}stats allocation to core and
convert veth & vrf"), stats allocation could be done on net core
instead of this driver.

With this new approach, the driver doesn't have to bother with error
handling (allocation failure checking, making sure free happens in the
right spot, etc). This is core responsibility now.

Remove the allocation in the xfrm driver and leverage the network
core allocation.
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/xfrm/xfrm_interface_core.c

@@ -240,7 +240,6 @@ static void xfrmi_dev_free(struct net_device *dev)
 	struct xfrm_if *xi = netdev_priv(dev);
 
 	gro_cells_destroy(&xi->gro_cells);
-	free_percpu(dev->tstats);
 }
 
 static int xfrmi_create(struct net_device *dev)
@@ -749,6 +748,7 @@ static void xfrmi_dev_setup(struct net_device *dev)
 	dev->flags 		= IFF_NOARP;
 	dev->needs_free_netdev	= true;
 	dev->priv_destructor	= xfrmi_dev_free;
+	dev->pcpu_stat_type	= NETDEV_PCPU_STAT_TSTATS;
 	netif_keep_dst(dev);
 
 	eth_broadcast_addr(dev->broadcast);
@@ -765,15 +765,9 @@ static int xfrmi_dev_init(struct net_device *dev)
 	struct net_device *phydev = __dev_get_by_index(xi->net, xi->p.link);
 	int err;
 
-	dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
-	if (!dev->tstats)
-		return -ENOMEM;
-
 	err = gro_cells_init(&xi->gro_cells, dev);
-	if (err) {
-		free_percpu(dev->tstats);
+	if (err)
 		return err;
-	}
 
 	dev->features |= NETIF_F_LLTX;
 	dev->features |= XFRMI_FEATURES;