x86: export pci-nommu's alloc_coherent

This patch exports nommu_alloc_coherent (renamed
dma_generic_alloc_coherent). GART needs this function.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
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 f408e6d..3b808e9 100644
--- a/include/asm-x86/dma-mapping.h
+++ b/include/asm-x86/dma-mapping.h
@@ -89,6 +89,9 @@
 extern int dma_supported(struct device *hwdev, u64 mask);
 extern int dma_set_mask(struct device *dev, u64 mask);
 
+extern void *dma_generic_alloc_coherent(struct device *dev, size_t size,
+					dma_addr_t *dma_addr, gfp_t flag);
+
 static inline dma_addr_t
 dma_map_single(struct device *hwdev, void *ptr, size_t size,
 	       int direction)