niu: Use eth_skb_pad helper

Replace the standard layout for padding an ethernet frame with the
eth_skb_pad call.
Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sun/niu.c

@@ -6651,13 +6651,8 @@ static netdev_tx_t niu_start_xmit(struct sk_buff *skb,
 		return NETDEV_TX_BUSY;
 	}
 
-	if (skb->len < ETH_ZLEN) {
-		unsigned int pad_bytes = ETH_ZLEN - skb->len;
-
-		if (skb_pad(skb, pad_bytes))
+	if (eth_skb_pad(skb))
 		goto out;
-		skb_put(skb, pad_bytes);
-	}
 
 	len = sizeof(struct tx_pkt_hdr) + 15;
 	if (skb_headroom(skb) < len) {