intel: add intel_handle

intel_handle is the base struct of any API handle, with its own helper
functions.  Move magic from intel_base to the new intel_handle.
diff --git a/icd/intel/obj.h b/icd/intel/obj.h
index 45b6586..83f4139 100644
--- a/icd/intel/obj.h
+++ b/icd/intel/obj.h
@@ -51,9 +51,7 @@
 };
 
 struct intel_base {
-    /* the loader expects a "void *" at the beginning */
-    void *loader_data;
-    uint32_t magic;
+    struct intel_handle handle;
 
     struct intel_base_dbg *dbg;
 
@@ -89,9 +87,6 @@
     obj->offset = offset;
 }
 
-bool intel_base_is_valid(const struct intel_base *base,
-                         XGL_DBG_OBJECT_TYPE type);
-
 XGL_RESULT intel_base_get_info(struct intel_base *base, int type,
                                size_t *size, void *data);