ixgbe: fix incorrect limit value in ring transverse

We were transversing the tx_ring with IXGBE_NUM_RX_QUEUES.  Now this define
happens to have the correct value but this is misleading and a change later
could easily make this no longer true.  I updated it to netdev->num_tx_queues
like we use in ixgbe_get_strings().

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c

@@ -1049,7 +1049,7 @@ static void ixgbe_get_ethtool_stats(struct net_device *netdev,
 		data[i] = (ixgbe_gstrings_stats[i].sizeof_stat ==
 		           sizeof(u64)) ? *(u64 *)p : *(u32 *)p;
 	}
-	for (j = 0; j < IXGBE_NUM_RX_QUEUES; j++) {
+	for (j = 0; j < netdev->num_tx_queues; j++) {
 		ring = adapter->tx_ring[j];
 		if (!ring) {
 			data[i] = 0;