iommu/arm-smmu: provide option to dsb macro when publishing tables

On coherent systems, publishing new page tables to the SMMU walker is
achieved with a dsb instruction. In fact, this can be a dsb(ishst) which
also provides the mandatory barrier option for arm64.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

drivers/iommu/arm-smmu.c

@@ -678,7 +678,7 @@ static void arm_smmu_flush_pgtable(struct arm_smmu_device *smmu, void *addr,
 
 	/* Ensure new page tables are visible to the hardware walker */
 	if (smmu->features & ARM_SMMU_FEAT_COHERENT_WALK) {
-		dsb();
+		dsb(ishst);
 	} else {
 		/*
 		 * If the SMMU can't walk tables in the CPU caches, treat them