x86: fix nommu_alloc_coherent allocation with NULL device argument

We need to use __GFP_DMA for NULL device argument (fallback_dev) with
pci-nommu. It's a hack for ISA (and some old code) so we need to use
GFP_DMA.

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>
diff --git a/include/asm-x86/dma-mapping.h b/include/asm-x86/dma-mapping.h
index 088c568..ad8b490 100644
--- a/include/asm-x86/dma-mapping.h
+++ b/include/asm-x86/dma-mapping.h
@@ -246,6 +246,8 @@
 	struct dma_mapping_ops *ops = get_dma_ops(dev);
 	void *memory;
 
+	gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
+
 	if (dma_alloc_from_coherent(dev, size, dma_handle, &memory))
 		return memory;