Update getSbeMeasurementRegisters() to handle CHIP_TARGET_SENTINEL
Update getSbeMeasurementRegisters() to handle CHIP_TARGET_SENTINEL

This commit fixes a bug on an early error path where
getSbeMeasurementRegisters() was called with the
MASTER_PROCESSOR_CHIP_TARGET_SENTINEL.  Now we look for this value
and skip some attribute lookups on it which we know will fail.

Change-Id: I97d90bb956aa686b31498828115c42e53a317d67
CQ:SW517462
Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/111728
Reviewed-by: Roland Veloz <768fb49134ab823c765de70e7067d9f65f5d0a3e@us.ibm.com>
Reviewed-by: Deborah L McLemore <1938e6bc52a6fb400ff401d42bc5360c2c7aaa30@us.ibm.com>
Reviewed-by: Daniel M Crowell <912029ca9254ac7b5854e56910561d682e1fa2d0@us.ibm.com>
Tested-by: Jenkins Server <8e3f934e4c44875bc48d33da3ea13d93ba9a233f@us.ibm.com>
Tested-by: Jenkins OP Build CI <e610bd72261d3c0a48f1e8ae36832ab00774d426@us.ibm.com>
Tested-by: FSP CI Jenkins <aa9e4d9ac7cd25905e9c0dd36d4150516e73dd86@us.ibm.com>
Tested-by: Jenkins OP HW <0eb0fff262f74a65a832afbcc7b153e391c9a3fd@us.ibm.com>

open-power/hostboot,open-power/hostboot,open-power/hostboot,open-power/hostboot,open-power/hostboot