x86: convert dma_alloc_coherent to use is_device_dma_capable

Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

include/asm-x86/dma-mapping.h

@@ -278,7 +278,7 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		gfp |= GFP_DMA;
 	}
 
-	if (!dev->dma_mask)
+	if (!is_device_dma_capable(dev))
 		return NULL;
 
 	if (!ops->alloc_coherent)