Secure Boot: Disable x-bus node communication

XBUS node communication using the XBUS mailbox is not allowed between
chips prior to SMP init when security is enabled; disable this until
it can be whollistically addressed

Change-Id: Ia032c635609e15629544926b7ff92537537d9325
RTC: 191008
CQ: SW431806
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/59808
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Reviewed-by: William G. Hoffa <wghoffa@us.ibm.com>
Tested-by: Jenkins OP Build CI <op-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP HW <op-hw-jenkins+hostboot@us.ibm.com>
Reviewed-by: Roland Veloz <rveloz@us.ibm.com>
Reviewed-by: Prachi Gupta <pragupta@us.ibm.com>
Reviewed-by: Nicholas E. Bofferding <bofferdn@us.ibm.com>

src/usr/isteps/istep09/call_proc_smp_link_layer.C

@@ -81,7 +81,11 @@ void*   call_proc_smp_link_layer( void    *io_pArgs )
 {
     errlHndl_t  l_errl  =   NULL;
     IStepError  l_StepError;
-    bool l_run_xbus_test = true;
+
+    // @TODO RTC:191008
+    // Currently the x-bus mailbox exchange causes a
+    // security violation in step 9, so disabling
+    bool l_run_xbus_test = false;
 
     TRACFCOMP( ISTEPS_TRACE::g_trac_isteps_trace,
                "call_proc_smp_link_layer entry" );