ia64: remove DMA_ERROR_CODE

All ia64 dma_mapping_ops instances already have a mapping_error member.
Signed-off-by: Christoph Hellwig <hch@lst.de>

arch/ia64/include/asm/dma-mapping.h

@@ -12,8 +12,6 @@
 
 #define ARCH_HAS_DMA_GET_REQUIRED_MASK
 
-#define DMA_ERROR_CODE 0
-
 extern const struct dma_map_ops *dma_ops;
 extern struct ia64_machine_vector ia64_mv;
 extern void set_iommu_machvec(void);