regulators: Add detectPhaseFaults() to Device

Add a detectPhaseFaults() method to the Device class.  This method
executes the PhaseFaultDetection data member added in a previous commit.

Add a gtest test case to exercise the new code.

Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
Change-Id: Ie8a2bf7d1b60ebc29c256e8563e3e4808bb6a20e
diff --git a/phosphor-regulators/src/device.hpp b/phosphor-regulators/src/device.hpp
index a8f35b6..c45f330 100644
--- a/phosphor-regulators/src/device.hpp
+++ b/phosphor-regulators/src/device.hpp
@@ -134,6 +134,20 @@
     void configure(Services& services, System& system, Chassis& chassis);
 
     /**
+     * Detect redundant phase faults in this device.
+     *
+     * Does nothing if phase fault detection is not defined for this device.
+     *
+     * This method should be called every 15 seconds.
+     *
+     * @param services system services like error logging and the journal
+     * @param system system that contains the chassis
+     * @param chassis chassis that contains the device
+     */
+    void detectPhaseFaults(Services& services, System& system,
+                           Chassis& chassis);
+
+    /**
      * Returns the configuration changes to apply to this device, if any.
      *
      * @return Pointer to Configuration object.  Will equal nullptr if no