Fixed XML output displayed by sadf (hugepages statistics were

Fixed XML output displayed by sadf (hugepages statistics were
included in power management ones).

When displaying stats with sar, hugepages utilization statistics
were displayed between voltage inputs statistics and CPU clock
ones. This was not really smart but still OK.
Yet, when displaying XML output with sadf -x, hugepages statistics
were included in the <power-management> section, which is quite bad
in this case. So move hugepage structure just after memory utilization
one in activity.c:act[] array.