arm64: device: add iommu pointer to device archdata

When using an IOMMU for device mappings, it is necessary to keep a
pointer between the device and the IOMMU to which it is attached in
order to obtain the correct IOMMU when attaching the device to a domain.

This patch adds an iommu pointer to the dev_archdata structure, in a
similar manner to other architectures (ARM, PowerPC, x86, ...).
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/device.h

@@ -18,6 +18,9 @@
 
 struct dev_archdata {
 	struct dma_map_ops *dma_ops;
+#ifdef CONFIG_IOMMU_API
+	void *iommu;			/* private IOMMU data */
+#endif
 };
 
 struct pdev_archdata {