cpuidle: Set residency to 0 if target Cstate not enter

When cpuidle governor choose a C-state to enter for idle CPU, but it notice that
there is tasks request to be executed. So the idle CPU will not really enter
the target C-state and go to run task.

In this situation, it will use the residency of previous really entered target
C-states. Obviously, it is not reasonable.

So, this patch fix it by set the target C-state residency to 0.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Youquan Song <youquan.song@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>