Fix formatting to help hostboot's attribute generation scripts

Hostboot looks for 0x when computing hex values. Adding 0x to a value
in this file that was missing.

Change-Id: I8d14721d17918d9ee661fdaae4cc434bdb853b8b
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/41772
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: Hostboot CI <hostboot-ci+hostboot@us.ibm.com>
Reviewed-by: JACOB L. HARVEY <jlharvey@us.ibm.com>
Reviewed-by: ANDRE A. MARIN <aamarin@us.ibm.com>
Reviewed-by: STEPHEN GLANCY <sglancy@us.ibm.com>
Reviewed-by: Matt K. Light <mklight@us.ibm.com>
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>
Reviewed-by: Jennifer A. Stofer <stofer@us.ibm.com>
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/41789
Reviewed-by: Hostboot Team <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>
Reviewed-by: Christian R. Geddes <crgeddes@us.ibm.com>

src/import/chips/p9/procedures/xml/attribute_info/memory_mrw_attributes.xml

@@ -67,7 +67,7 @@
     </description>
     <valueType>uint64</valueType>
     <mssUnits>cW</mssUnits>
-    <default>ffffe000000006A4</default>
+    <default>0xffffe000000006A4</default>
     <array>10</array>
     <platInit/>
     <initToZero/>