Add iomux_from_timers() function to recover an IOMux from

the associated UCTimers

src/iomux_impl.c

@@ -168,3 +168,8 @@ struct UCTimers *iomux_get_timers(struct IOMux *mux)
     return &mux->timers;
 }
 
+struct IOMux *iomux_from_timers(struct UCTimers *timers)
+{
+    return (struct IOMux*)timers; //timers is the 1. member of IOMux
+}
+