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>
diff --git a/arch/x86/pci/sta2x11-fixup.c b/arch/x86/pci/sta2x11-fixup.c
index ec008e8..53d6002 100644
--- a/arch/x86/pci/sta2x11-fixup.c
+++ b/arch/x86/pci/sta2x11-fixup.c
@@ -26,6 +26,7 @@
 #include <linux/pci_ids.h>
 #include <linux/export.h>
 #include <linux/list.h>
+#include <asm/iommu.h>
 
 #define STA2X11_SWIOTLB_SIZE (4*1024*1024)
 extern int swiotlb_late_init_with_default_size(size_t default_size);
@@ -191,7 +192,7 @@ static const struct dma_map_ops sta2x11_dma_ops = {
 	.sync_sg_for_cpu = swiotlb_sync_sg_for_cpu,
 	.sync_sg_for_device = swiotlb_sync_sg_for_device,
 	.mapping_error = swiotlb_dma_mapping_error,
-	.dma_supported = NULL, /* FIXME: we should use this instead! */
+	.dma_supported = x86_dma_supported,
 };
 
 /* At setup time, we use our own ops if the device is a ConneXt one */