Fixes #3603: Move r28489 to v1.6 branch (register MXM to memhooks)

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Custom patch from ticket based on:

r28489 [[BR]]
Fix data corruption in MXM by registering to OPAL memory release hooks and removing any mappings created by mxm
Bring over improvement from the trunk for the gkcommit script.
Fixes #3612: Add missing common sm help message to v1.6