A unique value used by this host system to identify this
conceptual row in the 'xcmHrSystemFaultTable'.
Usage: Conforming implementations SHALL NOT 'reuse' values of
'xcmHrSystemFaultIndex' until its' 32-bit value wraps. Even in
the case of eventual wrap, the entries SHALL be strictly
sequenced by the associated value of 'xcmHrSystemFaultDate'.
Usage: Conforming implementations are strongly encouraged to
preserve the last used value of 'xcmHrSystemFaultIndex' across
system power cycles.