iommu/amd: Set AMD iommu callbacks for platform bus driver

AMD has more drivers will use ACPI to platform bus driver later,
all those devices need iommu support, for example: eMMC driver.

For latest AMD eMMC controller, it will utilize sdhci-acpi.c driver,
which will rely on platform bus to match device and driver, where we
will set 'dev' of struct platform_device as map_sg parameter passing
to iommu driver for DMA request, so the iommu-ops are needed on the
platform bus.

Signed-off-by: Wan Zongshun <Vincent.Wan@amd.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/amd_iommu.c

@@ -21,6 +21,7 @@
 #include <linux/pci.h>
 #include <linux/acpi.h>
 #include <linux/amba/bus.h>
+#include <linux/platform_device.h>
 #include <linux/pci-ats.h>
 #include <linux/bitmap.h>
 #include <linux/slab.h>
@@ -2958,6 +2959,9 @@ int __init amd_iommu_init_api(void)
 	if (err)
 		return err;
 #endif
+	err = bus_set_iommu(&platform_bus_type, &amd_iommu_ops);
+	if (err)
+		return err;
 	return 0;
 }