psu-ng: Refactor VOUT_UV_FAULT detection

Split off code checking for VOUT_UV fault in STATUS_WORD to its own
function.

Change-Id: I3b5e898a7d4f1ad21317c66b7fcb97c211581dcd
Signed-off-by: Brandon Wyman <bjwyman@gmail.com>
diff --git a/phosphor-power-supply/power_supply.hpp b/phosphor-power-supply/power_supply.hpp
index ae4a02c..1e1e0fe 100644
--- a/phosphor-power-supply/power_supply.hpp
+++ b/phosphor-power-supply/power_supply.hpp
@@ -520,6 +520,15 @@
     void analyzeIoutOCFault();
 
     /**
+     * @brief Examines STATUS_WORD value read to see if there is a UV fault.
+     *
+     * Checks if the VOUT bit is on, indicating "An output voltage fault or
+     * warning has occurred", if it is on, but VOUT_OV_FAULT is off, it is
+     * determined to be an indication of an output under-voltage fault.
+     */
+    void analyzeVoutUVFault();
+
+    /**
      * @brief Examine STATUS_WORD for temperature fault.
      */
     void analyzeTemperatureFault();