x86: move pci-nommu's dma_mask check to common code

The check to see if dev->dma_mask is NULL in pci-nommu is more
appropriate for dma_alloc_coherent().

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/pci-nommu.c

@@ -80,9 +80,6 @@ nommu_alloc_coherent(struct device *hwdev, size_t size,
 	int node;
 	struct page *page;
 
-	if (hwdev->dma_mask == NULL)
-		return NULL;
-
 	gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
 	gfp |= __GFP_ZERO;
 

include/asm-x86/dma-mapping.h

@@ -254,6 +254,9 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		gfp |= GFP_DMA;
 	}
 
+	if (!dev->dma_mask)
+		return NULL;
+
 	if (ops->alloc_coherent)
 		return ops->alloc_coherent(dev, size,
 				dma_handle, gfp);