Make overrideOnly fapi attributes volatile-zero

Changing the volatility of platInit+overrideOnly ekb attributes
to be volatile-zero so that they don't take up any space in the
PNOR.  They will only be volatile (current setting) if they have
an explicit default value set.

Change-Id: Idff90d8d7062a360cc0ac1e0b365e3ea59d50d8f
Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/72736
Reviewed-by: Christian R. Geddes <crgeddes@us.ibm.com>
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP Build CI <op-jenkins+hostboot@us.ibm.com>
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP HW <op-hw-jenkins+hostboot@us.ibm.com>
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>

src/usr/targeting/xmltohb/fapi_utils.pl

@@ -183,7 +183,14 @@ (\%)
     {
         if( exists $fapiattr->{overrideOnly} )
         {
-            $targattr->{persistency} = "volatile";
+            if( exists $fapiattr->{default} )
+            {
+                $targattr->{persistency} = "volatile";
+            }
+            else
+            {
+                $targattr->{persistency} = "volatile-zeroed";
+            }
         }
         else
         {