wifi: iwlwifi: restore missing initialization of async_handlers_list

wifi: iwlwifi: restore missing initialization of async_handlers_list

The initialization of async_handlers_list
was accidentally removed in a previous change.
This patch restores the missing initialization
to ensure proper handler registration.

Fixes: 6895d74c11d8 ("wifi: iwlwifi: mld: initialize regulatory early")
Signed-off-by: Itamar Shalev <itamar.shalev@intel.com>
Acked-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250423092503.35206-1-itamar.shalev@intel.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>