iwlwifi: clean up properly when registration with mac80211 fails

If registration with mac80211 fails, stop the thermal
throttling and testmode work that were previously started.

Signed-off-by: Meenakshi Venkataraman <meenakshi.venkataraman@intel.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>