cpuquiet: Update stats only on successful operations

Change-Id: I0584fba7458b3a860f9ab3751a8eb5f0345864ad
Signed-off-by: Sai Charan Gurrappadi <sgurrappadi@nvidia.com>
Reviewed-on: http://git-master/r/111285
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Yu-Huan Hsu <yhsu@nvidia.com>