cpupower: Enable disabled Cstates if they are below max latency

cpupower idle-set -D <latency>
currently only disables all C-states that have a higher latency than the
specified <latency>. But if deep sleep states were already disabled and
have a lower latency, they should get enabled again.

For example:
This call:
cpupower idle-set -D 30
disables all C-states with a higher or equal latency than 30.
If one then calls:
cpupower idle-set -D 100
C-states with a latency between 30-99 will get enabled again with this patch
now. It is ensured that only C-states with a latency of 100 and higher are
disabled.

Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>