iommu/tegra-smmu: Use non-secure register for flushing

Use PTB_ASID instead of SMMU_CONFIG to flush smmu.
PTB_ASID can be accessed from non-secure mode, SMMU_CONFIG cannot be.
Using SMMU_CONFIG could pose a problem when kernel doesn't have secure
mode access enabled from boot.
Signed-off-by: Navneet Kumar <navneetk@nvidia.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/tegra-smmu.c

@@ -240,7 +240,7 @@ static inline void smmu_flush_tlb_group(struct tegra_smmu *smmu,
 
 static inline void smmu_flush(struct tegra_smmu *smmu)
 {
-	smmu_readl(smmu, SMMU_CONFIG);
+	smmu_readl(smmu, SMMU_PTB_ASID);
 }
 
 static int tegra_smmu_alloc_asid(struct tegra_smmu *smmu, unsigned int *idp)