arm64: remove the dummy_dma_ops mapping_error method

Just return DMA_MAPPING_ERROR from __dummy_map_page and let the core
dma-mapping code handle the rest.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arm64/mm/dma-mapping.c

@@ -119,7 +119,7 @@ static dma_addr_t __dummy_map_page(struct device *dev, struct page *page,
 				   enum dma_data_direction dir,
 				   unsigned long attrs)
 {
-	return 0;
+	return DMA_MAPPING_ERROR;
 }
 
 static void __dummy_unmap_page(struct device *dev, dma_addr_t dev_addr,
@@ -154,11 +154,6 @@ static void __dummy_sync_sg(struct device *dev,
 {
 }
 
-static int __dummy_mapping_error(struct device *hwdev, dma_addr_t dma_addr)
-{
-	return 1;
-}
-
 static int __dummy_dma_supported(struct device *hwdev, u64 mask)
 {
 	return 0;
@@ -176,7 +171,6 @@ const struct dma_map_ops dummy_dma_ops = {
 	.sync_single_for_device = __dummy_sync_single,
 	.sync_sg_for_cpu        = __dummy_sync_sg,
 	.sync_sg_for_device     = __dummy_sync_sg,
-	.mapping_error          = __dummy_mapping_error,
 	.dma_supported          = __dummy_dma_supported,
 };
 EXPORT_SYMBOL(dummy_dma_ops);