r8169: fix offloaded tx checksum for small packets.

The workaround introduced by commit e5195c1f 'r8169: fix 8168evl
frame padding.' upstream was incorrect and was entirely replaced in
commit b423e9ae 'r8169: fix offloaded tx checksum for small
packets.'

On the 3.2.y branch, the first commit has effectively been applied
twice: the first time by itself, and the second time in commit
3cf40360 which squashed the two upstream commits together.  That
left us with both the incorrect and the correct workaround in place.
Remove the incorrect one.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Francois Romieu <romieu@fr.zoreil.com>

drivers/net/ethernet/realtek/r8169.c

@@ -5584,14 +5584,6 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
 		goto err_stop_0;
 	}
 
-	/* 8168evl does not automatically pad to minimum length. */
-	if (unlikely(tp->mac_version == RTL_GIGA_MAC_VER_34 &&
-		     skb->len < ETH_ZLEN)) {
-		if (skb_padto(skb, ETH_ZLEN))
-			goto err_update_stats;
-		skb_put(skb, ETH_ZLEN - skb->len);
-	}
-
 	if (unlikely(le32_to_cpu(txd->opts1) & DescOwn))
 		goto err_stop_0;