arm: remove arch specific dma_supported implementation

And instead wire it up as method for all the dma_map_ops instances.

Note that the code seems a little fishy for dmabounce and iommu, but
for now I'd like to preserve the existing behavior 1:1.

Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 8f2c5a8..b9677ad 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -199,6 +199,7 @@
 	.sync_sg_for_cpu	= arm_dma_sync_sg_for_cpu,
 	.sync_sg_for_device	= arm_dma_sync_sg_for_device,
 	.mapping_error		= arm_dma_mapping_error,
+	.dma_supported		= arm_dma_supported,
 };
 EXPORT_SYMBOL(arm_dma_ops);
 
@@ -218,6 +219,7 @@
 	.map_page		= arm_coherent_dma_map_page,
 	.map_sg			= arm_dma_map_sg,
 	.mapping_error		= arm_dma_mapping_error,
+	.dma_supported		= arm_dma_supported,
 };
 EXPORT_SYMBOL(arm_coherent_dma_ops);
 
@@ -1184,11 +1186,10 @@
  * during bus mastering, then you would pass 0x00ffffff as the mask
  * to this function.
  */
-int dma_supported(struct device *dev, u64 mask)
+int arm_dma_supported(struct device *dev, u64 mask)
 {
 	return __dma_supported(dev, mask, false);
 }
-EXPORT_SYMBOL(dma_supported);
 
 #define PREALLOC_DMA_DEBUG_ENTRIES	4096
 
@@ -2149,6 +2150,7 @@
 	.unmap_resource		= arm_iommu_unmap_resource,
 
 	.mapping_error		= arm_dma_mapping_error,
+	.dma_supported		= arm_dma_supported,
 };
 
 const struct dma_map_ops iommu_coherent_ops = {
@@ -2167,6 +2169,7 @@
 	.unmap_resource	= arm_iommu_unmap_resource,
 
 	.mapping_error		= arm_dma_mapping_error,
+	.dma_supported		= arm_dma_supported,
 };
 
 /**