net: ethernet: ixp4xx: Make use of dma_pool_zalloc() instead of dma_pool_alloc/memset()

Replacing dma_pool_alloc/memset() with dma_pool_zalloc()
to simplify the code.
Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/xscale/ixp4xx_eth.c

@@ -1103,10 +1103,9 @@ static int init_queues(struct port *port)
 			return -ENOMEM;
 	}
 
-	if (!(port->desc_tab = dma_pool_alloc(dma_pool, GFP_KERNEL,
-					      &port->desc_tab_phys)))
+	port->desc_tab = dma_pool_zalloc(dma_pool, GFP_KERNEL, &port->desc_tab_phys);
+	if (!port->desc_tab)
 		return -ENOMEM;
-	memset(port->desc_tab, 0, POOL_ALLOC_SIZE);
 	memset(port->rx_buff_tab, 0, sizeof(port->rx_buff_tab)); /* tables */
 	memset(port->tx_buff_tab, 0, sizeof(port->tx_buff_tab));