iwlwifi: dvm: fix delayed enter to CT-kill bug

Theoretically, the card may not enter CTKILL:
In case the timer that iwl_prepare_ct_kill_task is setting,
will expire before tt->state revert to its previous state.

Signed-off-by: Eytan Lifshitz <eytan.lifshitz@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>