r6040: fix typo on stats update in tx path

We are currently updating the rx fifo error counter in the tx path while
it should have been the tx fifo error counter, fix that.
Signed-off-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/rdc/r6040.c

@@ -605,7 +605,7 @@ static void r6040_tx(struct net_device *dev)
 		err = ioread16(ioaddr + MLSR);
 
 		if (err & 0x0200)
-			dev->stats.rx_fifo_errors++;
+			dev->stats.tx_fifo_errors++;
 		if (err & (0x2000 | 0x4000))
 			dev->stats.tx_carrier_errors++;