wifi: iwlwifi: mld: make iwl_mld_add_all_rekeys void

No one checks its return value anyway.

Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250612144708.4c38fb4c48f4.Ia62100a54370b6af5e528ba10c8f21e177018096@changeid