wifi: iwlwifi: mvm: cleanup iwl_mvm_sta_del

wifi: iwlwifi: mvm: cleanup iwl_mvm_sta_del

Now it neither sets the ret argument or return something else than
false.
Cleanup this function to be void and to not receive the ret argument.
This also allows to get rid of the sta_in_fw parameter in
iwl_mvm_mld_free_sta_link.

Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Link: https://patch.msgid.link/20241224192322.ecebfa16c62c.Ia1cc352b871593be4f51cb3db98f9eedd5267857@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>