[S390] appldata: fix dev_get_stats 64 bit conversion

Fix this warning:

arch/s390/appldata/appldata_net_sum.c: In function 'appldata_get_net_sum_data':
arch/s390/appldata/appldata_net_sum.c:89: warning: initialization from incompatible pointer type

which was introduced with be1f3c2c
"net: Enable 64-bit net device statistics on 32-bit architectures"
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/appldata/appldata_net_sum.c

@@ -85,9 +85,10 @@ static void appldata_get_net_sum_data(void *data)
 
 	rcu_read_lock();
 	for_each_netdev_rcu(&init_net, dev) {
+		const struct rtnl_link_stats64 *stats;
 		struct rtnl_link_stats64 temp;
-		const struct net_device_stats *stats = dev_get_stats(dev, &temp);
 
+		stats = dev_get_stats(dev, &temp);
 		rx_packets += stats->rx_packets;
 		tx_packets += stats->tx_packets;
 		rx_bytes   += stats->rx_bytes;