Fix failures to boot with unsecured mode

Fixes the problem of slave SBEs causing hangs due to propagation
of istep mode bit of ATTR_BOOT_FLAGS.

Change-Id: I3c7ebe5626b6fbfb54e40a78c7d2ec69d2bde5df
CQ:SW413592
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/52267
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: HWSV CI <hwsv-ci+hostboot@us.ibm.com>
Tested-by: Hostboot CI <hostboot-ci+hostboot@us.ibm.com>
Reviewed-by: Nicholas E. Bofferding <bofferdn@us.ibm.com>
Reviewed-by: Sachin Gupta <sgupta2m@in.ibm.com>
Reviewed-by: Thi N. Tran <thi@us.ibm.com>
Reviewed-by: Jennifer A. Stofer <stofer@us.ibm.com>
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/52409
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: Christian R. Geddes <crgeddes@us.ibm.com>

src/import/chips/p9/procedures/hwp/perv/p9_setup_sbe_config.C

@@ -5,7 +5,7 @@
 /*                                                                        */
 /* OpenPOWER HostBoot Project                                             */
 /*                                                                        */
-/* Contributors Listed Below - COPYRIGHT 2015,2017                        */
+/* Contributors Listed Below - COPYRIGHT 2015,2018                        */
 /* [+] International Business Machines Corp.                              */
 /*                                                                        */
 /*                                                                        */
@@ -326,6 +326,10 @@ fapi2::ReturnCode p9_setup_sbe_config(const
         }
         else
         {
+            //Zero out the istep mode bit for slave chips to avoid hangs
+#ifdef __HOSTBOOT_MODULE
+            l_read_scratch_reg.clearBit<0>();
+#endif
             //Setting SCRATCH_REGISTER_3 register value
             //CFAM.SCRATCH_REGISTER_3 = l_read_scratch_reg
             FAPI_TRY(fapi2::putCfamRegister(i_target_chip, PERV_SCRATCH_REGISTER_3_FSI,