swiotlb: use map_single instead of swiotlb_map_single in swiotlb_alloc_coherent

We always need swiotlb memory here so address_needs_mapping and
swiotlb_force testings are irrelevant. map_single should be used here
instead of swiotlb_map_single.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

lib/swiotlb.c

@@ -483,12 +483,9 @@ swiotlb_alloc_coherent(struct device *hwdev, size_t size,
 		 * swiotlb_map_single(), which will grab memory from
 		 * the lowest available address range.
 		 */
-		dma_addr_t handle;
-		handle = swiotlb_map_single(NULL, NULL, size, DMA_FROM_DEVICE);
-		if (swiotlb_dma_mapping_error(hwdev, handle))
+		ret = map_single(hwdev, NULL, size, DMA_FROM_DEVICE);
+		if (!ret)
 			return NULL;
-
-		ret = bus_to_virt(handle);
 	}
 
 	memset(ret, 0, size);