stmmac: replace open coded __netdev_alloc_skb_ip_align() with actual call

This also matches with the sibling call netdev_alloc_skb_ip_align() made in
rx fast path.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -975,13 +975,11 @@ static int stmmac_init_rx_buffers(struct stmmac_priv *priv, struct dma_desc *p,
 {
 	struct sk_buff *skb;
 
-	skb = __netdev_alloc_skb(priv->dev, priv->dma_buf_sz + NET_IP_ALIGN,
-				 flags);
+	skb = __netdev_alloc_skb_ip_align(priv->dev, priv->dma_buf_sz, flags);
 	if (!skb) {
 		pr_err("%s: Rx init fails; skb is NULL\n", __func__);
 		return -ENOMEM;
 	}
-	skb_reserve(skb, NET_IP_ALIGN);
 	priv->rx_skbuff[i] = skb;
 	priv->rx_skbuff_dma[i] = dma_map_single(priv->device, skb->data,
 						priv->dma_buf_sz,