MDIA: For OCMBs avoid getting parent chip

Change-Id: I08a982751cae186755dcd6c136c4bbb040f80b6b
CQ: SW489852
Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/95129
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP Build CI <op-jenkins+hostboot@us.ibm.com>
Reviewed-by: Benjamen G Tyner <ben.tyner@ibm.com>
Reviewed-by: Brian J Stegmiller <bjs@us.ibm.com>
Tested-by: Jenkins OP HW <op-hw-jenkins+hostboot@us.ibm.com>
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Reviewed-by: Zane C Shelley <zshelle@us.ibm.com>

src/usr/diag/mdia/mdiamba.C

@@ -5,7 +5,7 @@
 /*                                                                        */
 /* OpenPOWER HostBoot Project                                             */
 /*                                                                        */
-/* Contributors Listed Below - COPYRIGHT 2012,2018                        */
+/* Contributors Listed Below - COPYRIGHT 2012,2020                        */
 /* [+] International Business Machines Corp.                              */
 /*                                                                        */
 /*                                                                        */
@@ -48,11 +48,14 @@ bool __nimbusDD1Workaround( TargetHandle_t i_trgt )
 
     bool slowRead = false;
 
-    ConstTargetHandle_t parent = getParentChip( i_trgt );
+    TARGETING::Target* masterProc = nullptr;
+    TARGETING::targetService().masterProcChipTargetHandle(masterProc);
 
     // The workaround only applies to Nimbus
-    if ( MODEL_NIMBUS == parent->getAttr<ATTR_MODEL>() )
+    if ( MODEL_NIMBUS == masterProc->getAttr<ATTR_MODEL>() )
     {
+        ConstTargetHandle_t parent = getParentChip( i_trgt );
+
         // check if DD1.x
         if ( 0x20 > parent->getAttr<ATTR_EC>() )
         {