iommu/arm-smmu: Constify some helpers

Sprinkle a few `const`s where helpers don't need write access.
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Will Deacon <will@kernel.org>

drivers/iommu/arm/arm-smmu/arm-smmu.h

@@ -377,7 +377,7 @@ struct arm_smmu_master_cfg {
 	s16				smendx[];
 };
 
-static inline u32 arm_smmu_lpae_tcr(struct io_pgtable_cfg *cfg)
+static inline u32 arm_smmu_lpae_tcr(const struct io_pgtable_cfg *cfg)
 {
 	u32 tcr = FIELD_PREP(ARM_SMMU_TCR_TG0, cfg->arm_lpae_s1_cfg.tcr.tg) |
 		FIELD_PREP(ARM_SMMU_TCR_SH0, cfg->arm_lpae_s1_cfg.tcr.sh) |
@@ -398,13 +398,13 @@ static inline u32 arm_smmu_lpae_tcr(struct io_pgtable_cfg *cfg)
 	return tcr;
 }
 
-static inline u32 arm_smmu_lpae_tcr2(struct io_pgtable_cfg *cfg)
+static inline u32 arm_smmu_lpae_tcr2(const struct io_pgtable_cfg *cfg)
 {
 	return FIELD_PREP(ARM_SMMU_TCR2_PASIZE, cfg->arm_lpae_s1_cfg.tcr.ips) |
 	       FIELD_PREP(ARM_SMMU_TCR2_SEP, ARM_SMMU_TCR2_SEP_UPSTREAM);
 }
 
-static inline u32 arm_smmu_lpae_vtcr(struct io_pgtable_cfg *cfg)
+static inline u32 arm_smmu_lpae_vtcr(const struct io_pgtable_cfg *cfg)
 {
 	return ARM_SMMU_VTCR_RES1 |
 	       FIELD_PREP(ARM_SMMU_VTCR_PS, cfg->arm_lpae_s2_cfg.vtcr.ps) |