PNOR: implement Software RedundancyPriority interface.

- Create override function for redundancepriority.
- Update RedundancyPriority for image that holds that
  already holds the requested priority.

Resolves openbmc/openbmc#1553

Change-Id: I1a5c35826c881f6e9e21550c664b033c6f4b4bc0
Signed-off-by: Saqib Khan <khansa@us.ibm.com>
diff --git a/item_updater.hpp b/item_updater.hpp
index 233f022..6409698 100755
--- a/item_updater.hpp
+++ b/item_updater.hpp
@@ -41,6 +41,15 @@
         {
         }
 
+        /** @brief Sets the given priority free by incrementing
+         *  any existing priority with the same value by 1
+         *
+         *  @param[in] value - The priority that needs to be set free.
+         *
+         *  @return None
+         */
+        void freePriority(uint8_t value);
+
     private:
         /** @brief Callback function for Software.Version match.
          *  @details Creates an Activation dbus object.