mask core SPATTN bit used for core checkstop handshake

Change-Id: I9c0a7224c3880ab40bb9111d8f66449912029e2f
CQ: SW431474
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/59707
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Reviewed-by: Thi N. Tran <thi@us.ibm.com>
Reviewed-by: James N. Klazynski <jklazyns@us.ibm.com>
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: PPE CI <ppe-ci+hostboot@us.ibm.com>
Reviewed-by: Jennifer A. Stofer <stofer@us.ibm.com>
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/59713
Reviewed-by: Sachin Gupta <sgupta2m@in.ibm.com>

src/import/chips/p9/procedures/hwp/core/p9_hcd_core_scomcust.C

@@ -74,6 +74,8 @@ p9_hcd_core_scomcust(
     l_data64.flush<0>().setBit(EX_CPPM_CPMMR_WKUP_NOTIFY_SELECT);
     FAPI_TRY(putScom(i_target, C_CPPM_CPMMR_CLEAR, l_data64));
 
+    FAPI_TRY(putScom(i_target, C_SPATTN_MASK, 0x2222222200000000ULL));
+
 fapi_try_exit:
 
     FAPI_INF("<<p9_hcd_core_scomcust");