powerpc: Add iommu domain pointer to device archdata

Add an iommu domain pointer to device (powerpc) archdata.  Devices
are attached to iommu domains and this pointer provides a mechanism
to correlate between a device and the associated iommu domain.  This
field is set when a device is attached to a domain.
Signed-off-by: Varun Sethi <Varun.Sethi@freescale.com>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Joerg Roedel <joro@8bytes.org>

arch/powerpc/include/asm/device.h

@@ -28,6 +28,9 @@ struct dev_archdata {
 		void		*iommu_table_base;
 	} dma_data;
 
+#ifdef CONFIG_IOMMU_API
+	void			*iommu_domain;
+#endif
 #ifdef CONFIG_SWIOTLB
 	dma_addr_t		max_direct_dma_addr;
 #endif