wifi: iwlwifi: mvm: remove pre-mld code from mld path

wifi: iwlwifi: mvm: remove pre-mld code from mld path

This code is only relevant for older devices, that are not supporting
mld, so shouldn't be in iwl_mvm_sta_del, which is common to both pre-mld
and mld.

Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Link: https://patch.msgid.link/20241224192322.a665d16a3857.I840b00a7b38f3967ec5e75ff6a85e756f4d82437@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>