iwlwifi: mvm: reset the temperature when temperature test is disabled

Since we can't read the actual temperature when the firmware is
running, just set the temperature to 0 when the test is disabled and
disable CT Kill if it was enabled.

Additionally, since we rely on iwl_mvm_tt_handler() to exit CT kill
when in test mode, call iwl_mvm_exit_ctkill() in that function if the
temperature is low again.  Also make the iwl_mvm_enter_ctkill() and
iwl_mvm_exit_ctkill() return if called when not necessary anymore
(e.g. when iwl_mvm_exit_ctkill() is called when we're not in CT-kill).

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>