BMC: Implement Software RedundancyPriority.interface

- Create Redundancy Priority interface after a successful
  PNOR update and set the priority.
- Remove Redundancy Priority interface once the activation
  state changes from being Active.
- Create override function for RedundancyPriority.

Resolves openbmc/openbmc#1755

Change-Id: I160dc4a6cad243d58759c71bbeb218aab841cf7a
Signed-off-by: Saqib Khan <khansa@us.ibm.com>
diff --git a/item_updater.hpp b/item_updater.hpp
index fb8e9df..75b2a68 100644
--- a/item_updater.hpp
+++ b/item_updater.hpp
@@ -54,6 +54,15 @@
             processBMCImage();
         };
 
+    /** @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);
+
     /**
      * @brief Create and populate the active BMC Version.
      */