net: hix5hd2_gmac: Remove unneeded cast from memory allocation

Remove casting the values returned by memory allocation function.

Coccinelle emits WARNING:

./drivers/net/ethernet/hisilicon/hix5hd2_gmac.c:1027:9-23: WARNING:
 casting value returned by memory allocation function to (struct sg_desc *) is useless.

This issue was detected by using the Coccinelle software.
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hix5hd2_gmac.c

@@ -1024,9 +1024,9 @@ static int hix5hd2_init_sg_desc_queue(struct hix5hd2_priv *priv)
 	struct sg_desc *desc;
 	dma_addr_t phys_addr;
 
-	desc = (struct sg_desc *)dma_alloc_coherent(priv->dev,
-				TX_DESC_NUM * sizeof(struct sg_desc),
-				&phys_addr, GFP_KERNEL);
+	desc = dma_alloc_coherent(priv->dev,
+				  TX_DESC_NUM * sizeof(struct sg_desc),
+				  &phys_addr, GFP_KERNEL);
 	if (!desc)
 		return -ENOMEM;