powerpc: implement ->mapping_error

DMA_ERROR_CODE is going to go away, so don't rely on it.  Instead
define a ->mapping_error method for all IOMMU based dma operation
instances.  The direct ops don't ever return an error and don't
need a ->mapping_error method.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/iommu.h

@@ -139,6 +139,8 @@ struct scatterlist;
 
 #ifdef CONFIG_PPC64
 
+#define IOMMU_MAPPING_ERROR		(~(dma_addr_t)0x0)
+
 static inline void set_iommu_table_base(struct device *dev,
 					struct iommu_table *base)
 {
@@ -238,6 +240,8 @@ static inline int __init tce_iommu_bus_notifier_init(void)
 }
 #endif /* !CONFIG_IOMMU_API */
 
+int dma_iommu_mapping_error(struct device *dev, dma_addr_t dma_addr);
+
 #else
 
 static inline void *get_iommu_table_base(struct device *dev)