regulators: Add monitorSensors support to Rail

Implemented the monitorSensors() method in the Rail class.  This method
reads the sensors for a voltage rail.

Signed-off-by: Bob King <Bob_King@wistron.com>
Change-Id: Ifbe6461349d20fee1eba233844c95c1046e1a54a
diff --git a/phosphor-regulators/src/rail.hpp b/phosphor-regulators/src/rail.hpp
index 9e0ce3d..8340d07 100644
--- a/phosphor-regulators/src/rail.hpp
+++ b/phosphor-regulators/src/rail.hpp
@@ -102,6 +102,20 @@
     }
 
     /**
+     * Monitor the sensors for this rail.
+     *
+     * Sensor monitoring is optional.  If sensor monitoring is defined for this
+     * rail, the sensor values are read.
+     *
+     * This method should be called once per second.
+     *
+     * @param system system that contains the chassis
+     * @param chassis chassis that contains the device
+     * @param device device that contains this rail
+     */
+    void monitorSensors(System& system, Chassis& chassis, Device& device);
+
+    /**
      * Returns the sensor monitoring for this rail, if any.
      *
      * @return Pointer to SensorMonitoring object.  Will equal nullptr if no