arm64: remove DMA_ERROR_CODE

The dma alloc interface returns an error by return NULL, and the
mapping interfaces rely on the mapping_error method, which the dummy
ops already implement correctly.

Thus remove the DMA_ERROR_CODE define.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index 3216e09..147fbb9 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -184,7 +184,6 @@ static void *__dma_alloc(struct device *dev, size_t size,
 no_map:
 	__dma_free_coherent(dev, size, ptr, *dma_handle, attrs);
 no_mem:
-	*dma_handle = DMA_ERROR_CODE;
 	return NULL;
 }
 
@@ -487,7 +486,7 @@ static dma_addr_t __dummy_map_page(struct device *dev, struct page *page,
 				   enum dma_data_direction dir,
 				   unsigned long attrs)
 {
-	return DMA_ERROR_CODE;
+	return 0;
 }
 
 static void __dummy_unmap_page(struct device *dev, dma_addr_t dev_addr,