x86: remove arch specific dma_supported implementation

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

Note that this also means the arch specific check will be fully instead
of partially applied in the AMD iommu driver.

Signed-off-by: Christoph Hellwig <hch@lst.de>

arch/x86/kernel/pci-calgary_64.c

@@ -493,6 +493,7 @@ static const struct dma_map_ops calgary_dma_ops = {
 	.map_page = calgary_map_page,
 	.unmap_page = calgary_unmap_page,
 	.mapping_error = calgary_mapping_error,
+	.dma_supported = x86_dma_supported,
 };
 
 static inline void __iomem * busno_to_bbar(unsigned char num)