add admin message for calibration.

meshtastic/admin.proto

@@ -241,6 +241,11 @@ message AdminMessage {
      */
     string delete_file_request = 22;
 
+    /*
+     * Set zero and offset for scale chips
+     */
+    uint32 set_scale = 23;
+
     /*
      * Set the owner for this node
      */