x86: fix dma_mapping_error for 32bit x86, cleanup

This removes ifdef CONFIG_X86_64 in dma_mapping_error():

1) Xen people plan to use swiotlb on X86_32 for Dom0 support. swiotlb
   uses ops->mapping_error so X86_32 also needs to check
   ops->mapping_error.

2) Removing #ifdef hack is almost always a good thing.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/include/asm/dma-mapping.h

@@ -71,12 +71,10 @@ static inline struct dma_mapping_ops *get_dma_ops(struct device *dev)
 /* Make sure we keep the same behaviour */
 static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
 {
-#ifdef CONFIG_X86_64
 	struct dma_mapping_ops *ops = get_dma_ops(dev);
 	if (ops->mapping_error)
 		return ops->mapping_error(dev, dma_addr);
 
-#endif
 	return (dma_addr == bad_dma_address);
 }