openrisc: remove DMA_ERROR_CODE

openrisc does not return errors for dma_map_page.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

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

@@ -26,8 +26,6 @@
 #include <linux/kmemcheck.h>
 #include <linux/dma-mapping.h>
 
-#define DMA_ERROR_CODE		(~(dma_addr_t)0x0)
-
 extern const struct dma_map_ops or1k_dma_map_ops;
 
 static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)