intel: hide intel_cmd_reloc

And mark intel_mem in it const.
diff --git a/icd/intel/cmd_pipeline.c b/icd/intel/cmd_pipeline.c
index f49dbb8..ca3c2db 100644
--- a/icd/intel/cmd_pipeline.c
+++ b/icd/intel/cmd_pipeline.c
@@ -113,7 +113,7 @@
 }
 
 static void gen6_3DSTATE_INDEX_BUFFER(struct intel_cmd *cmd,
-                                      struct intel_mem *mem,
+                                      const struct intel_mem *mem,
                                       XGL_GPU_SIZE offset,
                                       XGL_INDEX_TYPE type,
                                       bool enable_cut_index)