Fix MBS mask FIR for Obus recovery

Sets the external timeout FIR to be masked off.

Change-Id: I17095b43962ad9e8df694b91cc391829a99b500b
CQ:SW432572
RTC:194981
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/60211
Reviewed-by: Louis Stermole <stermole@us.ibm.com>
Reviewed-by: Marc Gollub <gollub@us.ibm.com>
Reviewed-by: ANDRE A. MARIN <aamarin@us.ibm.com>
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Dev-Ready: STEPHEN GLANCY <sglancy@us.ibm.com>
Tested-by: Hostboot CI <hostboot-ci+hostboot@us.ibm.com>
Reviewed-by: Edgar R. Cordero <ecordero@us.ibm.com>
Reviewed-by: Jennifer A. Stofer <stofer@us.ibm.com>
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/60219
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: Daniel M. Crowell <dcrowell@us.ibm.com>

src/import/chips/centaur/procedures/hwp/memory/p9c_mss_unmask_errors.C

@@ -361,7 +361,7 @@ fapi2::ReturnCode unmask_inband_errors_helper(const fapi2::Target<fapi2::TARGET_
     l_mbs_fir_action1.clearBit<2>();
     l_mbs_fir_mask_or.setBit<2>();
 
-    // 3    external_timeout        recoverable         mask (until unmask_fetch_errors)
+    // 3    external_timeout        masked off as request for Obus cable recovery support
     l_mbs_fir_action0.clearBit<3>();
     l_mbs_fir_action1.setBit<3>();
     l_mbs_fir_mask_or.setBit<3>();
@@ -2247,8 +2247,7 @@ fapi2::ReturnCode mss_unmask_fetch_errors(const fapi2::Target<fapi2::TARGET_TYPE
     // 2    invalid_address_error   channel checkstop   unmask
     l_mbs_fir_mask_and.clearBit<2>();
 
-    // 3    external_timeout        recoverable         unmask
-    l_mbs_fir_mask_and.clearBit<3>();
+    // 3    external_timeout        MASKED         - Don't touch! per needing this masked off for Obus recovery
 
     // 4    internal_timeout        recoverable         unmask
     l_mbs_fir_mask_and.clearBit<4>();