drm/msm: make iommu port names const'ier

Signed-off-by: Rob Clark <robdclark@gmail.com>
diff --git a/drivers/gpu/drm/msm/msm_mmu.h b/drivers/gpu/drm/msm/msm_mmu.h
index 7cd88d9..b8ca9a0 100644
--- a/drivers/gpu/drm/msm/msm_mmu.h
+++ b/drivers/gpu/drm/msm/msm_mmu.h
@@ -21,8 +21,8 @@
 #include <linux/iommu.h>
 
 struct msm_mmu_funcs {
-	int (*attach)(struct msm_mmu *mmu, const char **names, int cnt);
-	void (*detach)(struct msm_mmu *mmu, const char **names, int cnt);
+	int (*attach)(struct msm_mmu *mmu, const char * const *names, int cnt);
+	void (*detach)(struct msm_mmu *mmu, const char * const *names, int cnt);
 	int (*map)(struct msm_mmu *mmu, uint32_t iova, struct sg_table *sgt,
 			unsigned len, int prot);
 	int (*unmap)(struct msm_mmu *mmu, uint32_t iova, struct sg_table *sgt,