tg3: Fix stats while interface is down

If the tg3 interface is down, the driver will return ethtool stats
uninitialized.  This patch zeroes out the destination stat buffer in
such a case.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/tg3.c

@@ -10154,9 +10154,6 @@ static struct tg3_ethtool_stats *tg3_get_estats(struct tg3 *tp,
 	struct tg3_ethtool_stats *old_estats = &tp->estats_prev;
 	struct tg3_hw_stats *hw_stats = tp->hw_stats;
 
-	if (!hw_stats)
-		return old_estats;
-
 	ESTAT_ADD(rx_octets);
 	ESTAT_ADD(rx_fragments);
 	ESTAT_ADD(rx_ucast_packets);
@@ -11029,7 +11026,10 @@ static void tg3_get_ethtool_stats(struct net_device *dev,
 {
 	struct tg3 *tp = netdev_priv(dev);
 
-	tg3_get_estats(tp, (struct tg3_ethtool_stats *)tmp_stats);
+	if (tp->hw_stats)
+		tg3_get_estats(tp, (struct tg3_ethtool_stats *)tmp_stats);
+	else
+		memset(tmp_stats, 0, sizeof(struct tg3_ethtool_stats));
 }
 
 static __be32 *tg3_vpd_readblock(struct tg3 *tp, u32 *vpdlen)