amd-xgbe: use dma_mapping_error to check map errors

The dma_mapping_error() returns true or false, but we want
to return -ENOMEM if there was an error.

Fixes: 174fd259 ("amd-xgbe: Implement split header receive support")
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/amd/xgbe/xgbe-desc.c

@@ -289,7 +289,7 @@ static int xgbe_alloc_pages(struct xgbe_prv_data *pdata,
 	struct page *pages = NULL;
 	dma_addr_t pages_dma;
 	gfp_t gfp;
-	int order, ret;
+	int order;
 
 again:
 	order = alloc_order;
@@ -316,10 +316,9 @@ static int xgbe_alloc_pages(struct xgbe_prv_data *pdata,
 	/* Map the pages */
 	pages_dma = dma_map_page(pdata->dev, pages, 0,
 				 PAGE_SIZE << order, DMA_FROM_DEVICE);
-	ret = dma_mapping_error(pdata->dev, pages_dma);
-	if (ret) {
+	if (dma_mapping_error(pdata->dev, pages_dma)) {
 		put_page(pages);
-		return ret;
+		return -ENOMEM;
 	}
 
 	pa->pages = pages;