net: calxedaxgmac: drop some unnecessary register writes

The interrupts have already been cleared, so we don't need to clear them
again. Also, we could miss interrupts if they are cleared, but we don't
process the packet.
Signed-off-by: NRob Herring <rob.herring@calxeda.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/calxeda/xgmac.c

@@ -846,9 +846,6 @@ static void xgmac_free_dma_desc_rings(struct xgmac_priv *priv)
 static void xgmac_tx_complete(struct xgmac_priv *priv)
 {
 	int i;
-	void __iomem *ioaddr = priv->base;
-
-	writel(DMA_STATUS_TU | DMA_STATUS_NIS, ioaddr + XGMAC_DMA_STATUS);
 
 	while (dma_ring_cnt(priv->tx_head, priv->tx_tail, DMA_TX_RING_SZ)) {
 		unsigned int entry = priv->tx_tail;
@@ -1139,9 +1136,6 @@ static int xgmac_rx(struct xgmac_priv *priv, int limit)
 		struct sk_buff *skb;
 		int frame_len;
 
-		writel(DMA_STATUS_RI | DMA_STATUS_NIS,
-		       priv->base + XGMAC_DMA_STATUS);
-
 		entry = priv->rx_tail;
 		p = priv->dma_rx + entry;
 		if (desc_get_owner(p))