PEL: Simplify addLocationCodePrefix

Location codes can either start with Ufcs, Umts, or the same but with
the fcs and mts characters already substituted in with the real VPD
fields.  Update the addLocationCodePrefix() prefix function to not add
the prefix if the location code starts with a 'U', which could mean any
of the 4 cases above.

At this time this isn't absolutely necessary; it is more for future
proofing.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I1aae7e21b14fe22ea8d4b651546ce26d25aacd86
diff --git a/extensions/openpower-pels/data_interface.hpp b/extensions/openpower-pels/data_interface.hpp
index 4883338..944de05 100644
--- a/extensions/openpower-pels/data_interface.hpp
+++ b/extensions/openpower-pels/data_interface.hpp
@@ -551,9 +551,10 @@
     }
 
     /**
-     * @brief Adds the Ufcs- prefix to the location code passed in.
+     * @brief Adds the Ufcs- prefix to the location code passed in
+     *        if necessary.
      *
-     * Necessary because the location codes that come back from the
+     * Needed because the location codes that come back from the
      * message registry and device callout JSON don't have it.
      *
      * @param[in] - The location code without a prefix, like P1-C1