iommu: Introduce accessors for iommu private data

Add dev_iommu_priv_get/set() functions to access per-device iommu
private data. This makes it easier to move the pointer to a different
location.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Tested-by: Will Deacon <will@kernel.org> # arm-smmu
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/20200326150841.10083-9-joro@8bytes.org

include/linux/iommu.h

@@ -627,6 +627,16 @@ static inline void dev_iommu_fwspec_set(struct device *dev,
 	dev->iommu->fwspec = fwspec;
 }
 
+static inline void *dev_iommu_priv_get(struct device *dev)
+{
+	return dev->iommu->fwspec->iommu_priv;
+}
+
+static inline void dev_iommu_priv_set(struct device *dev, void *priv)
+{
+	dev->iommu->fwspec->iommu_priv = priv;
+}
+
 int iommu_probe_device(struct device *dev);
 void iommu_release_device(struct device *dev);