iommu/tegra: Use helper functions to access dev->iommu_fwspec

Use the new helpers dev_iommu_fwspec_get()/set() to access
the dev->iommu_fwspec pointer. This makes it easier to move
that pointer later into another struct.

Cc: Thierry Reding <thierry.reding@gmail.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/tegra-smmu.c

@@ -846,7 +846,7 @@ static struct iommu_group *tegra_smmu_group_get(struct tegra_smmu *smmu,
 
 static struct iommu_group *tegra_smmu_device_group(struct device *dev)
 {
-	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
+	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
 	struct tegra_smmu *smmu = dev->archdata.iommu;
 	struct iommu_group *group;