regulators: Add monitorSensors support to Chassis

Implemented the monitorSensors() method in the Chassis class.  This method
reads the sensors for the voltage rails produced by the chassis.

Signed-off-by: Bob King <Bob_King@wistron.com>
Change-Id: Idb283b09c645983190601e030334399ee76c1995
diff --git a/phosphor-regulators/src/chassis.hpp b/phosphor-regulators/src/chassis.hpp
index 3fd3792..4423926 100644
--- a/phosphor-regulators/src/chassis.hpp
+++ b/phosphor-regulators/src/chassis.hpp
@@ -122,6 +122,16 @@
         return number;
     }
 
+    /**
+     * Monitors the sensors for the voltage rails produced by this chassis, if
+     * any.
+     *
+     * This method should be called once per second.
+     *
+     * @param system system that contains the chassis
+     */
+    void monitorSensors(System& system);
+
   private:
     /**
      * Chassis number within the system.