PEL: Add SRC callouts from message registry

When an SRC is being built for a new PEL, it will now also add callouts
from the message registry JSON for that error.

This commit only adds support for callouts of maintenance procedures or
symbolic FRUs.  A future commit will add support for calling out a
regular piece of hardware

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I78c0d3440c748f21145d452742e3aa682f26003b
diff --git a/extensions/openpower-pels/data_interface.hpp b/extensions/openpower-pels/data_interface.hpp
index 5b6ff94..6a3e326 100644
--- a/extensions/openpower-pels/data_interface.hpp
+++ b/extensions/openpower-pels/data_interface.hpp
@@ -226,6 +226,18 @@
                                     std::string& ccin,
                                     std::string& serialNumber) const = 0;
 
+    /**
+     * @brief Gets the system type from Entity Manager
+     *
+     * @param[in] std::string - The system type string
+     */
+    virtual std::string getSystemType() const
+    {
+        // TODO, not implemented by entity manager yet, but adding now
+        // so it can be mocked.
+        return _systemType;
+    }
+
   protected:
     /**
      * @brief Sets the host on/off state and runs any
@@ -326,6 +338,11 @@
      * @brief The motherboard CCIN
      */
     std::string _motherboardCCIN;
+
+    /**
+     * @brief The system type
+     */
+    std::string _systemType;
 };
 
 /**